I had the same. Just before Fable became available, I was working on a document building on a ton of research that I wasn't entirely sure about (I don't think it counts as research itself, except in the Facebook sense). I had Opus and Gemini review it a couple of times until they and I thought it looked pretty good. Then Fable appeared, I had it review it, and it still found a ton of errors.

It's definitely good. Or at least it was. I'm not sure how badly they nerfed it.