So I've noticed this happen once every so often and I can't make any sense of it so now I'm just going to post it. I think it generally happens when updating a feature, although I can't be certain if that is always the case.
It goes like this:
1: Do a basic feature like a cut
2: Close out feature
3: Do some other things
4: Realize you need to tweak that feature you did a little while ago
5: Go change it
6: Get a warning dialogue telling you that the feature didn't work
7: Clearly it did
SOLUTION:
Delete feature; redo.
It's happened a handful of times, and those models just have a forever yellow/red feature that's actually fine.
