I don't know what it is with Gemini (and even other models) but I swear they must be doing some kind of active load-dependant quanitization or a/b/c/d testing behind the scenes, because sometimes the model is stellar and hitting everything, and other times it's tripping all over itself.

The most effective fix I have found is that when the model is acting dumb, just turn it off and come back in the few hours to a new chat and try again.

Yeah I think they all shed under heavy load as part of some scaling strategy.