It depends on the severity and who is getting it. Sometimes you get more of just a pull on the threads, you can find them if you look for them. If it's for me, then it's usually good enough. I have a lot of problems with me/my machine doing small loops and going up and backwards, that's when I get that sort of thing.
Other times you get noticeable loops you can feel or can get fingers/toes caught in, those need to go. I cut out the stitches and repair just those areas, trying to go in a different direction than I did before.
I mark the areas to redo with safety pins, means there is something I need to do there.
And sometimes the whole back of the quilt looks like a caterpillar nest. Nothing to do in that case but take it all out once you are done crying....