[Question]
  [
Your input is a list/sequence/vector/array of 5-255 positive integers, not necessarily unique. You may assume whatever input format is most suitable, and that each integer (as well as the quantity of integers) is chosen uniformly at random from the range 5-255.
The goal is to output the same list, in the same (or equivalent) format, but sorted into increasing (nondecreasing) order. A common early exercise in learning a language. Submissions to include:
1. An answer which works correctly and achieves the goal; and
2. A second answer which contains an annoying bug. Between 1% and 10% of the time, the output needs to be a list in the correct format and containing the correct elements, but *in the wrong order* (any order except correctly sorted). The rest of the time, the program must work correctly and achieve the goal.
The two answers must have [Levenshtein distance](https://en.wikipedia.org/wiki/Levenshtein_distance) one; that is, we can get one from the other by deleting one byte, or adding one byte, or changing one byte.
Scoring as usual in code-golf (based on the shorter of your two answers), with usual loopholes forbidden.
10% bonus (decrease to score) if the annoying bug is input-independent, i.e. using the same input again doesn't reproduce the bug (except between 1% and 10% of the time).
  
[Answer]
# [Python 3](https://docs.python.org/3/), 36 bytes
## Bug-free version, 37 bytes
```
lambda l:sorted(l,reverse=l[-9:]==[])
```
[Try it online!](https://tio.run/##bY7BCsIwEETv@Yq1pwRrrUoPBnLxN2qRaFMNpEnZpoKI3x4TK3jxtLAzb2aGh785uwudOAYj@3MrwfDRoVctNTmqu8JRCVOv9rwRom5Y0P0QZUBpW9eTi5usBwElIZ1D0KBtkq6KbsqScQImivVsLtLR1tMq31YVgwScfsBfE2sIYIzoqGEE5raliK@FgO9MZIQMmJDsMF05PF/r2J0VMb6Xnn4YxsIb "Python 3 – Try It Online")
## Annoying version, 36 bytes
```
lambda l:sorted(l,reverse=l[9:]==[])
```
[Try it online!](https://tio.run/##bY7NCsIwEITv@xRrTwmWWpUeDOTia9Qi0aY1kJ@SpoKIzx5TK3jxtLAz38wMj3Bzdh87fopamEsrULPR@SBbonMv79KPkuv6wBrO64ZGZYakohe2dQaubrIBOZYAnfOoUNlZ6iXZliVlgDqJ9WIu5qNsIFW@qyqKM3D@AX9NtAH0KaIjmgIubWueXiuO35WeAgx@RrLj1DN8vjapOytSvBGBfBhK4xs "Python 3 – Try It Online")
This depends on the input and therefore does not qualify for the bonus.  
It has a probability of around 2% to fail. It fails when the input length is lower then 10.
Combined with [LyricLy's answer](https://codegolf.stackexchange.com/a/147094/64121) this gets 34 bytes:
```
lambda l:sorted(l)[::l[9:]>[]or 1]
lambda l:sorted(l)[::l[9:]>[]or-1]
```
[Answer]
# [05AB1E](https://github.com/Adriandmen/05AB1E), 5\*0.9 = 4.5 bytes
**Working solution**
```
{TLΩi
```
[Try it online!](https://tio.run/##MzBNTDJM/W9oYOD2vzrE59zKzP@1Ov@jjXTMzHWMjXTMdQyNjHVMTICUjmksAA "05AB1E – Try It Online")
**Explanation**
```
{      # sort input
 TL    # push the range [1 ... 10]
   Ω   # pick a random number in the range
    i  # if true (equal to 1), do nothing
```
**Solution containing the bug**
Gives the wrong solution 10% of the time (independent on input).
```
{TLΩiR
```
[Try it online!](https://tio.run/##MzBNTDJM/W9oYOD2vzrE59zKzKD/tTr/o410zMx1jI10zHUMjYx1TEyAlI5pLAA "05AB1E – Try It Online")
**Explanation**
Same as the working solution, except it reverses the list if the number picked is true.
[Answer]
# [Jelly](https://github.com/DennisMitchell/jelly), 7 \* (100% - 10%) = 6.3 bytes
```
Ṣ¹⁵X:¤¡
```
[Try it online!](https://tio.run/##y0rNyan8///hzkWHdj5q3BphdWjJoYX/wx/u6j6x3ehwu7fKo6Y1kf//R1vqKBjqKBjpKBgDGQYGQKY5iGVqEAsA "Jelly – Try It Online")
Buggy version:
```
ṢẊ⁵X:¤¡
```
[Try it online!](https://tio.run/##y0rNyan8///hzkUPd3U9atwaYXVoyaGF/8Mf7uo@sd3ocLu3yqOmNZH//0db6igY6igY6SgYAxkGBkCmOYhlahALAA "Jelly – Try It Online")
In both links, there's a test harness that will run the code 100 times, each time with the list you give as the argument, and then return the results.
The probability of each input length is:
```
0.1 - 0.1/(length!)
```
So for length 1 there's a 0% probability, for length 2 5%, for length 3 8.83̅%, for length 4 9.583̅% etc. until length ∞ which has a 10% probability.
[Answer]
# Python 3, score ~~58~~ 57 - 10% = 51.3
Saved a byte thanks to ovs.
### Bug-free version, 57 bytes
```
lambda m:sorted(m)[::random()>.1or 1]
from random import*
```
[Try it online!](https://tio.run/##K6gsycjPM/6fZhvzPycxNyklUSHXqji/qCQ1RSNXM9rKqigxLyU/V0PTTs8wv0jXMJYrrSg/VwEiqpCZWwBUqvW/oCgzr0QjTSPaUEfBREfBXEfBCMiI1dT8DwA "Python 3 – Try It Online")
### Bugged version, 57 bytes
```
lambda m:sorted(m)[::random()>.1or-1]
from random import*
```
[Try it online!](https://tio.run/##K6gsycjPM/6fZhvzPycxNyklUSHXqji/qCQ1RSNXM9rKqigxLyU/V0PTTs8wv0jBMJYrrSg/VwEiqpCZWwBUqvW/oCgzr0QjTSPaUEfBREfBXEfBCMiI1dT8DwA "Python 3 – Try It Online")
I decided to try a solution that uses the bonus. It doesn't beat the other Python answer, but I had fun thinking it up.
[Answer]
# C, 71\*0.9 = 63.9 bytes
**Bug-free:**
```
c(int*a,int*b){return*a-*b;}f(a,n)int*a;{if(rand()%1<9)qsort(a,n,4,c);}
```
[Try it online!](https://tio.run/##hVDBaoNAFLz7FYMQ2GdW0LSRtqv00l4baHMLOZhVyx6iVje9iN9udzdioRD6Dg9mZ9/MeyPDTymnSTJV6yDntp9o6Ep96eogD4OTGCuW85ocLwZVsS6vC0arOH2kr77ptKX5PZckxum7UQV02WtG3uDBlJmDPsTJUThYNR2sF1QWCag0TgTWa0WOtKUP6ogMW6wxG222kfCuw0xzxAnN0MrILOJojdb/6sPi0XbmT8X81V0BnztLEgurKjC3RYqWzLj8pdrMElc8ut5edM8knuEjxNtuj4/d@/71xceTe5mRUR89zy52zlW9ZNO7C7U6lywiunHC5uFvQi5eozj9AA)
**Buggy:**
```
c(int*a,int*b){return*a-*b;}f(a,n)int*a;{if(rand()%10<9)qsort(a,n,4,c);}
```
[Try it online!](https://tio.run/##hVDBaoNAFLz7FYMQ2GdW0LSRtqv00l4baHMLOZhVyx6iVje9iN9udzdioRD6Dg9mZ9/MeyPDTymnSTJV6yDntp9o6Ep96eogD4OTGCuW85ocLwZVsS6vC0arOEof6atvOm15fs8liXH6blQBXfaakTd4MGUGoQ9xchQOVk0HawaVRQIqjROB9VqRI23pgzoiwxZrzE6bbSS86zDTHHFCM7QyMos4WqP1v/qweLSd@VMxf3VXwOfOksTCqgrMbZGiJTMuf6k2s8QVj663F90ziWf4CPG22@Nj975/ffHx5F5mZNRHz7OLnXNVL9n07kKtziWLiG6csHn4m5CL1yhOPw)
[Answer]
# [Groovy](http://groovy-lang.org/), 31 bytes
**Bugged solution:**
```
{a->a.sort()[a[9]?0..-1:-1..0]}
```
**Working solution:**
```
{a->a.sort()[a[0]?0..-1:-1..0]}
```
The Groovy subscript operator (the `getAt` method) returns null for lists if the index is bigger than the size. So if there's a ninth element it'll stay the same as the sorted list, but if not (1.99203187% chance) it'll be reversed. However there will always be a first element because the list's size is always bigger than or equal to 5. So the 0 in `a[0]` could be swapped with 1, 2, 3 or 4.
[Answer]
# [Wolfram Language (Mathematica)](https://www.wolfram.com/wolframscript/), 29 bytes
This is 26.1 bytes with the bonus, but I'm not entirely sure I earn the bonus; on already-sorted input, both versions always produce sorted output.
## Bug-free version (29 bytes)
```
If[RandomReal[]<0.,#,Sort@#]&
```
[Try it online!](https://tio.run/##y00syUjNTSzJTE78H1CUmVcS/d8zLTooMS8lPzcoNTEnOtbGQE9HWSc4v6jEQTlW7T9UzjOvJDU9tSi62lTHyNS0VgeraCwQ/AcA "Wolfram Language (Mathematica) – Try It Online")
## Annoying version (30 bytes)
```
If[RandomReal[]<0.1,#,Sort@#]&
```
[Try it online!](https://tio.run/##y00syUjNTSzJTE78H1CUmVcS/d8zLTooMS8lPzcoNTEnOtbGQM9QR1knOL@oxEE5Vu0/VNIzryQ1PbUoutpUx8jUtFYHq2gsEPwHAA "Wolfram Language (Mathematica) – Try It Online")
[Answer]
# PHP, 70 bytes
## Bug-free version, 70 bytes
```
<?unset($argv[0]);((rand(1,9)?"":r).sort)($argv);echo join(" ",$argv);
```
[Try it online!](https://tio.run/##K8go@P/fxr40rzi1REMlsSi9LNogVtNaQ6MoMS9Fw1DHUtNeScmqSFOvOL@oRBOiQtM6NTkjXyErPzNPQ0lBSQcq@P//fyPT/4Zm/02BNJBhavjf2Oy/pSVQ6F9@QUlmfl7xf908AA)
## Bugged version, 70 bytes
```
<?unset($argv[0]);((rand(0,9)?"":r).sort)($argv);echo join(" ",$argv);
```
[Try it online!](https://tio.run/##K8go@P/fxr40rzi1REMlsSi9LNogVtNaQ6MoMS9Fw0DHUtNeScmqSFOvOL@oRBOiQtM6NTkjXyErPzNPQ0lBSQcq@P//fyPT/4Zm/02BNJBhavjf2Oy/pSVQ6F9@QUlmfl7xf908AA)
The bugged version sorts in reverse order 10% of the time (based on a random number generator).
[Answer]
# [Python 2](https://docs.python.org/2/), 26 bytes
Buggy:
```
lambda l:l[9:]and l.sort()
```
[Try it online!](https://tio.run/##K6gsycjPM/qfZhvzPycxNyklUSHHKifa0io2MS9FIUevOL@oREPzf1p@kUKOQmaeQnS0sY6hjpGOaaxOUWJeeqqGkYGOriEQacZacXEWFGXmlSjkcHGmaeRowrk66jF56v8B "Python 2 – Try It Online")
Outputs by [modifying the input list](https://codegolf.meta.stackexchange.com/a/4942/20260). Sorts the list only if its length is at least 10. The non-buggy version replaces the `9` with a `0` to always sort. 
Working:
```
lambda l:l[0:]and l.sort()
```
[Try it online!](https://tio.run/##PcexCoAgEADQub7ithSuKKNF6EvMwSgruM4wl77emoK3vOtJe2CV/Thlcue8OCBNptXW8QLU3CEmIbMPEQgOBmN67FDhYDE63lahWqy7j7S6LK54cAIqCy9I/sVq4iq/ "Python 2 – Try It Online")
We can modify the function to return the list at the cost of 4 bytes, for 30 bytes total:
```
lambda l:l[9:]and l.sort()or l
```
[Try it online!](https://tio.run/##FcRBCoAgEADAc71ijwpblNEhoZeYB6OsYFvDvPR6KxjmetIeWGU/TpncOS8OSJMZtHW8ANV3iEnIEIGy/4eDwZgOW1TYW4yOt1WoBqv2I60uiysenMALkvkF "Python 2 – Try It Online")
---
25 bytes with some stretches of the rules:
```
[list,sorted][id(0)%17>0]
```
[Try it online!](https://tio.run/##K6gsycjPM/qfZhvzPzons7hEpzi/qCQ1JTY6M0XDQFPV0NzOIPZ/QVFmXolCmka0sY6hjlGs5n8A "Python 2 – Try It Online")
Outputs a function literal that either sorts or is the identity, using `id(0)` as a random source. Change `>` to `>=` to fix, or `0` to `~0`.
[Answer]
# [Husk](https://github.com/barbuz/Husk), 6 bytes
Buggy version:
```
?OIV¦9
```
[Try it online!](https://tio.run/##DYuxDYAwEAMXcvH@hORTUVPR0SB6JErESgzCYo8r27rz@dxX5rwu2/eOzNydAVoDo4MVQbCrdYPXArKjNLhpTqbp4Ai0gAs2yaYcqOJFN5vAIod2/A "Husk – Try It Online")
Correct version:
```
?OIVK9
```
[Try it online!](https://tio.run/##DYsrDoBAEEMvVDGd/c0qNEHgMARPgiScf6hqm/d6f@@Tuezrsc3MPJ0BWgdjgBVBcKgNg9cCcqB0uGk203RwBnrABbtkU05U8aKbNbDIoV0/ "Husk – Try It Online")
## Explanation
These programs are completely deterministic.
In fact, Husk has currently no support at all for random numbers.
```
?  V    If any element
    ¦9  is divisible by 9 (in buggy version),
    K9  is truthy when replaced by 9 (in correct version),
 O      sort the list,
  I     otherwise return it unchanged.
```
I claim that the output of the buggy program is not sorted with a probability between 1% and 2%.
Denote by **N = 251** the number of possible values of the elements.
The probability that a random list of length **L** contains no multiples of 9 is **((N-K)/N)^L**, where **K** is the number of values divisible by 9 (in our case **K = 28**).
The total probability is the average of this for **5 ≤ L ≤ 255**, which is about 1.98%.
Some of these lists are false positives, since they are already sorted.
The probability of a random list of length **L** to be sorted is at most **((N+N\*(N-1)/2)/N^2)^⌊L/2⌋**: if we break the list into chunks of length 2, each of the **⌊L/2⌋** chunks must be sorted.
The total probability of a list being sorted is bounded by the average of the above for **5 ≤ L ≤ 255**, which is about 0.30%.
Thus the probability of the function returning a non-sorted list is between 1.67% and 1.98%.
[Answer]
# [Bash](https://www.gnu.org/software/bash/), 26 bytes
## Correct version
```
s=n
sort -${s:RANDOM%20<0}
```
[Try it online!](https://tio.run/##S0oszvj/v9g2j6s4v6hEQVelutgqyNHPxd9X1dDAxqD2/39LLkMuIy5jIDQ0MOAyMgfSpgYA) or [check the probabilities](https://tio.run/##Jc7BCoJAGATg@/8UP2qoiLQaEVoGQdcKumal6ZYe2s3d9dT27LYWc5jLBzO3UjZDxXumsogQAlWp1oo@X3DnAq/YMiwk7dD5kWKJNUdDcCTaG2TGQHKhMHTeMj1u9tvDbhKTFfkMvlYC3Zy5aAK0ajjUnFE9ct2ztsOw0pLWGAq0pH3BwDuRMDkHPgZ2Hk3/iynaD2tIIIIYZibmI8QL03PyBQ).
## Bugged version
```
s=n
sort -${s:RANDOM%20<1}
```
[Try it online!](https://tio.run/##S0oszvj/v9g2j6s4v6hEQVelutgqyNHPxd9X1cjAxrD2/39LLkMuIy5jIDQ0MOAyMgfSpgYA) or [check the probabilities](https://tio.run/##Jc7BCoJAGATg@/8UP2qoiLQaEVoGQdcKumal6ZYe2s3d9dT27LYWc5jLBzO3UjZDxXumsogQAlWp1oo@X3DnAq/YMiwk7dD5kWKJNUdDcCTaG2TGQHKhMHTeMj1u9tvDbhKTVfQZfK0Eujlz0QRo1XCoOaN65LpnbYdhpSWtMRRoSfuCgXciYXIOfAzsPJr@F1O0H9aQQAQxzEzMR4gXpufkCw).
Takes input as newline-separated numbers. Uses the builtin variable `RANDOM`, which [always returns a (pseudo)random number in the range 0 - 32767](http://tldp.org/LDP/abs/html/randomvar.html). Using `%20` results in about a 5% failure rate (thanks @Titus for clarifying issues with `%10`).
This randomness means the failure rate is independent of the input, but this does require that the input array includes at least one number with more than one digit, because the failure output is sorted lexicographically.
## Alternate version, 27 bytes
```
((RANDOM+20))||cat&&sort -n
```
Bugged version replaces the `+` with a `%`. [Try it online](https://tio.run/##JY6xCsIwGIT3PMWPlTYhBNOKSBUFwVUFV6u2ptF2MLFJuuXda6rccMP3wd2jss0gdK/cJuWcI1G5rZPvD3pqA3doFZRWdjD9KeUaag1BgVHxeMD4vDvuTweacUK8DySOrTYOmBqIdwaSQiUQgqRoNKq1kn7kvldtB0x4K2tgBiY2ugHFF87yKyVAoyKd/SdXEL0mQ45SlKF5SDiJsmXoBf8C) or [try it bugged](https://tio.run/##JY5BC4IwHMXv@xR/tHRDRtOIsCgIulbQNStNV3poy23e9t3XLN7hHX4/eO9R6dbVchBmkzLGUF2ZreHvD3pKBXfoBJSa9zD5KeUaGglegVGx2GF83h33p8M0Y4RY60kUaakMUOGINQriQsTgg3jdStRIwe3I7SC6HmhtNW@AKgh0eIMEXxjNrwmBJCzS2X9yBeErcDlKUYbmPv4kypa@F@wL).
[Answer]
# [Pyth](https://github.com/isaacg1/pyth), score 8 \* 0.9 = 7.2
First snippet (correct one):
```
h.uSNT.S
```
**[Try it here!](https://pyth.herokuapp.com/?code=h.uSNT.S&input=%5B1%2C5%2C3%2C9%2C2%5D&debug=0)**
Second snippet (bugged one):
```
O.uSNT.S
```
**[Try it here!](https://pyth.herokuapp.com/?code=O.uSNT.S&input=%5B1%2C5%2C3%2C9%2C2%5D&debug=0)**
Saved two bytes (and 1.8 score) thanks to [isaacg](https://codegolf.stackexchange.com/users/20080/isaacg)!
[Answer]
## JavaScript (ES6), 24 bytes
Bug-free version (at least for integers in the range 0-2147483647, so anything in the given range):
```
a=>a.sort((a,b)=>a-b>>0)
```
Buggy version:
```
a=>a.sort((a,b)=>a-b>>1)
```
Depends on a) the engine's sorting algorithm and b) the input list containing two values in the wrong order that differ by 1. (If the probability of that turns out to be too low then the `1` can be increased, but by the time you get to `8` it simply won't sort anything in the range `5-255`.)
[Answer]
# PHP, 62 bytes
inspired by [Jo´s solution](https://codegolf.stackexchange.com/a/147092/55735) (and I just noticed: it´s a port of [Justin Mariner´s](https://codegolf.stackexchange.com/a/147112/55735)):
working (sorts ascending):
```
unset($argv[0]);(r[rand()+20].sort)($argv);echo join(_,$argv);
```
buggy (approx. 5% chance of descending sort):
```
unset($argv[0]);(r[rand()%20].sort)($argv);echo join(_,$argv);
```
Run with `-nr`
[Answer]
# [Pushy](https://github.com/FTcode/Pushy), 9 bytes - 10% = 8.1
**Bugged Solution:**
```
g0TUn?};_
```
[**Try it online!**](https://tio.run/##Kygtzqj8/z/dICQ0z77WOv7////RhjoKpjoKJjoKxjoKZjoKhrEA "Pushy – Try It Online")
**Working Solution:**
```
g1TUn?};_
```
[**Try it online!**](https://tio.run/##Kygtzqj8/z/dMCQ0z77WOv7////RhjoKpjoKJjoKxjoKZjoKhrEA "Pushy – Try It Online")
The bugged code does the following:
```
g0TUn?};_
g          \ Sort the stack correctly
 0TU       \ Generate random(0, 10)
    n? ;   \ If this is zero:
      }    \    Cyclically shift the stack right once
        _  \ Print the result
```
The fixed code simply changes `0` to `1`. As `random(1, 10)` will never be `0`, the if statement will never be executed.
[Answer]
# [MATL](https://github.com/lmendo/MATL), ~~7\*0.9 = 6.3~~ 6\*0.9 = 5.4 bytes
Buggy version:
```
Gr.9<?S
```
[Try it online!](https://tio.run/##y00syfn/371Iz9LGPvj//2hTHRMdYx0jHcNYAA "MATL – Try It Online")
**Explanation:**
```
G        % Grab input
 r       % Push a random number between 0 and 1
  .9     % Push 0.9
    <    % Check if the random number is smaller than 0.9
     ?   % If true
      S  % Sort input
         % Implicit output
```
Bug-free version:
```
Gr9<?S
```
[Try it online!](https://tio.run/##y00syfn/P7hIz9LGPvj//2hTHRMdYx0jHcNYAA)
**Explanation:**
```
G       % Grab input
 r      % Push a random number between 0 and 1
  9     % Push 9
   <    % Check if the random number is smaller than 9 (always true)
    ?   % If true
     S  % Sort the input
        % Implicit output     
```
[Answer]
# [Jq 1.5](https://stedolan.github.io/jq/), 42 bytes
Buggy
```
sort|if length%13<=0then reverse else. end
```
Working (delete the =)
```
sort|if length%13<0then reverse else. end
```
Assuming line lengths are uniform in range [5,255] about 7% will trigger the bug
[Try it online!](https://tio.run/##bVLLjtowFN3zFUfASMlA3gRGDHxCN92mDDLEgTCJDbYzdCS@vfTGBqmLemXfx3lc39PlPsLpglJyDSENjuyLg2HX1Y1BLaCYKFF1Ym9qKaAlrhyd5jgac15GkZKaG8P2suShVIfoWn/W0U/qke1WdO2OKz06XQYjGIkDF1wxw5HEscWVLTGcOwOmFPvWkBUaLg7miDxI8xzXmq5frOlIm5Ny4C41KHkFwX@bbY@z/VHvSYiszHIAOmERb8A0xnvZCYMbBRIX0Ib4qeYGD16azOIkw@sj7GOCNM@SOEl8vICyi9lbNp@9YYRWlkg/ssS2Fg53kmCKcAovRIR5nmdzylWNlMrHBu9Wosq3pHb5P6lWVrbBGp4XFukmytLFfOG/pnl8cyiT/IlSMsM8x@pbi3X1MLdKYI5cgLdn891neKO5HQIdx@6Muxj5Hut@OhMKEbtvkw3TBs@CAorvO6W517PYUa4eJZbpAdrzOFZw2hCy/AQIC/eJwWPm4plo2dnrLUeR7fNpdGNB8X/tBYnvWxuifB8U8ZQwngW0NT5udy2VudXPTXlJstU6dsL4F20bt8rCHuDel4Xrdd/htA/l59ApH@5YiV9e6A9t5R957vdb34NAdE0T2LWkh2LXQHaGHn8B "jq – Try It Online")
[Answer]
# J, 22.5 bytes (25 bytes - 10%)
### with bug:
```
[:]`(1&A.)@.(0.1>?@0:)/:~
```
### without bug:
```
[:]`(0&A.)@.(0.1>?@0:)/:~
```
[Try it online!](https://tio.run/##y/qfVqxga6VgoADE/6OtYhM0DNUc9TQd9DQM9Azt7B0MrDT1rer@a3Ip6Smop9laqSvoKNRaKaQVc3Hl5ccnlaYr2OopgPUZYNHHxZWanJGvoJGmZKigYWhgoGCsYqJgrGCkqWmtAdGOIfEfAA "J – Try It Online")
[Answer]
# [R](https://www.r-project.org/), 30\*.9 = 27 bytes
(buggy)
```
function(l)sort(l,runif(1)<.1)
```
[Try it online!](https://tio.run/##K/qfpmCj@z@tNC@5JDM/TyNHszi/qEQjR6eoNC8zTcNQ007PUPP/fwA "R – Try It Online")
(not buggy)
```
function(l)sort(l,runif(1)<.0)
```
The buggy version sorts in `decreasing=T` 10% of the time, sampling from a uniform(0,1) distribution. The un-buggy version is always `decreasing=F`
[Answer]
# [Röda](https://github.com/fergusq/roda), 42 bytes - 10% = 37.8
Bug-free:
```
{sort key={|i|currentTime|[_%20//19*0+i]}}
```
Buggy:
```
{sort key={|i|currentTime|[_%20//19*i+i]}}
```
[Try it online!](https://tio.run/##Lc1BDoIwFATQdTnFmOhGm0BBTTThFu4qUSJt/LFQbWFhKGfHkrj4m5l5@c429dzW1GFMmMa5xHUevXU9XupbjoHCY3BOdf2FWhXkbZNnaSpOW9pRNU0z8@oDwSGyDAHaOhAamzAmj/zA97zgORfVUsXzQwvt@1IuwXswBiYu34N/QoA0JAxWJaSIqIj4wI8VqoQ1tlN/Hp2jrsd9fUuXn7omo5p7Ms0/ "Röda – Try It Online")
This uses the `currentTime` function to create random numbers. It seems that their distribution varies a little between machines. The ratio `20//19` can be adjusted to get different results for no byte penalty (unless it is smaller than `99//98`).
[Answer]
# [Octave](https://www.gnu.org/software/octave/), 36\*0.9 = 32.4 bytes
Buggy version:
```
@(x)sort(x)(shift(1:end,+(rand<.1)))
```
[Try it online!](https://tio.run/##DcoxCsAgDADArzgmVEIdXKRCvyLV0CxaVEp/nzrdcu2a6S3KkYj0hA9H63MB4xae4EKp2W7QU80HOURUbt2ImGhc8LvNMh7g9TyiXVd/ "Octave – Try It Online")
Bug-free version:
```
@(x)sort(x)(shift(1:end,+(rand<.0)))
```
[Try it online!](https://tio.run/##DcoxCsAgDADArzgmVEIdXKRCvyLV0CxaVEp/nzrdcu2a6S3KkYj0hA9H63MB4xae4EKp2W7QU80H7Yio3LoRMdG44HebZTzA63lEu67@)
This sorts the vector, then shifts all numbers one to the right if a random number is less than 0.1.
[Answer]
# Java 8, ~~45~~ 34.2 (~~50~~ 38 - 10%) bytes
**Normal version:**
```
a->{if(Math.random()>0.)a.sort(null);}
```
**Explanation:**
[Try it here.](https://tio.run/##lZBPS8QwEMXv@ynmmFo2FEEv3S14FNw9uEfxMLbpmtqmJZlWlqWfvU7/KBXdipAEMnkv7zeTYYPrslImS966OEfnYIfanFcA2pCyKcYK9v0VoCl1ArHI2CJr0rm8sxZPD9rR5p61R2UjQC9kbcublyMkHcMeDGyhw3V01qnYIb1KiyYpC@FFgfRQutKSMHWee2HbhaO3ql9y9k5fDNEFg4kDWW2OT8@cNFIt4ow5fY0JYquQ1ONQmhRfFjFwAxgZi5lpqh5OjlQhy5pkxfH0Q9KuemSrGw74ZF4EW2b5b2dGvf@qjoRgWu/7zK@ubwLPv51aS0vba0BvgxD05rKeX31/IoNZvMQk@TumHU6rqLZmzj4Or@0@AA)
```
a->{                    // Method with ArrayList<Integer> parameter and no return-type
  if(Math.random()>0.)  //  If the random 0-1 double is larger than 0:
    a.sort(null);       //   Sort the input-List
}                       // End of method
```
---
**Bugged version (~~51~~ 39 bytes):**
```
a->{if(Math.random()>0.1)a.sort(null);}
```
LD of 1: `1` added.
**Explanation:**
[Try it here.](https://tio.run/##lZBPT4QwEMXv@ynmWCTboIle2CXxaOLuwT0aD2MpaxEKKQNms@Gz4/BHg1ExJm2TTt/r@82k2OC6KLVN49dOZVhVsENjzysAY0m7BJWGfX8FaAoTgxIpW2RNJpO3zuHp3lS0uWPtUbsI0AtZ2/LmVRGSUbAHC1vocB2dTSJ2SC/SoY2LXHhRIC89lFXhSNg6y7yw7cLRXNbPGZunP4bsnMnEgZyxx8cnjhqxFnnGoL7GCMppJP0wlCbFp0UM4ABWKjEzTdXDqSKdy6ImWXI8fZO0qx7ZmYYDPpgXwZZZ/tuZ1W8/qiMhmNb7OvSLq@vA82@m1pLC9Row2yAEs/ldz6@@P5HBLF5iHP8d0w6n01Q7O2cfh9d27w)
```
a->{                     // Method with ArrayList<Integer> parameter and no return-type
  if(Math.random()>0.1)  //  If the random 0-1 double is larger than 0.1:
    a.sort(null);        //   Sort the input-List
}                        // End of method
```
[Answer]
JavaScript, 25\*0.9=22.5
```
new Date%25?x:x.sort()
```
input x
]