The problem is that it's sort of chicken-and-egg. It's virtually impossible to separate cause from effect. The fact that it happened in 2 stages, first getting erratic, then breaking pretty much (but not conclusively) rules out the twig theory, but there too, it could have bent, messing up the trim, and broken after riding this way a while.

Lesson to the OP, and anyone reading this. If something changes, ie bike suddenly develops a wobble, RD gets noisy, crank sarts ticking, etc...., then something changed, and needs to be attended to now not later, even if it's only to identify what changed and decide to fix it later.