From personal experience, yes: I've seen multiple cases of scientists finding the ultimate cause of their bugs was some fast-math-related optimization.
The problem isn't necessarily the code they wrote themselves: it is often that they've compiled someone else's code or an open source library with fast-math, which broke some internal piece.
The problem isn't necessarily the code they wrote themselves: it is often that they've compiled someone else's code or an open source library with fast-math, which broke some internal piece.