Sometimes, that's what needs to happen, and I'm sure that you're as dissatisfied with that as I would be, since it doesn't answer the question as to why it happened in the first place. A corrupted cache can cause all sorts of oddities. Not saying that's definitely what caused this, but IMO that's the most likely reason. I've gotten into the habit of clearing cache before working on any of my games or even playing in someone else's.