It quite frequently seems to get lost and mistakenly decide whole sections of code is a comment, or other similar mistakes that do not have an obvious cause.

I've come across that myself with Xcode, often when I'm adding strings or /* */ comment blocks. The code below shifts to reflect the change brought about by opening the quotes, but closing them doesn't propagate the change fully. I've found that opening and re-closing the comment/quotes typically jogs Xcode to do the right thing.