Unfortunately, it's back to being twisted up. I had to remove the rear wheel and went to put it back on and the chain managed to become all twisted up again. This time the bike was sat right-side up, it wasn't laid down on its side or (worse) upside down.

I know when my friend's friend worked on the bike, the only way we could get the chain untwisted was to actually break it off, take it off and straighten it out, put it back on and link it back together.

But it seems like it doesn't matter how careful I am - when I remove the rear wheel, the chain always manages to twist itself up like a pretzel. Could there be an explanation for why it keeps doing this. Anything to prevent it from happening in the future?