I had this experience with a particular React hook recently. We ended up with like 5 teams implementing very similar functionality, and then when developer #6

I had this experience with a particular React hook recently. We ended up with like 5 teams implementing very similar functionality, and then when developer #6 came along and tried to replace them all with a common implementation it broke 2 out of 5 use cases because of very subtle edge cases. I guess React runtime behavior is kind of high on the scale of how hard code is to reason about, so maybe this wouldn't happen in an easier codebase. But still a very instructive exercise.