If you have any question or find any problem doing the homeworks, you should always ask or report it.

Most likely, you won't face a bug in all homeworks. If you are lucky enough to come across one, specify enough detail for TA to replicate the bug, and you shouldn't spend any more time on it yourself. And as such, extra credits are rewarded only on a case by case basis, with 0 to 5% of the particular homework.

Btw, the homeworks are heavy, so it's always a good idea to start early.