I haven't seen it run into a ton of issues like this when it can see all of the files, but I did hit issues where it would make guesses about how e.g. the Stripe gem's API worked and they'd be wrong.
Overall with Rails though, testing has always been pretty important partly because of the lack of types. I have noticed Windsurf is pretty good at taking a controller or model and writing tests for it though!
With Ruby, it doesn't have as much information, so it has to rely on testing or linters for feedback.