I challenge you to explore different perspectives.
You are faced with a service that handles any codebase that's thrown at it with incredible ease, without requiring any tweaking or special prompting.
For some reason, the same system fails to handle your personal codebase.
What's the root cause? Does it lie in the system that works everywhere with anything you throw at it? Or is it in your codebase?
Note that language servers, static analysis tooling, and so on still work without issue.
The cause (which is my assumption) is that there aren't enough good examples in the training set for anything useful to be the most likely continuation thus leading to a suboptimal result given the domain. Thus the tool doesn't work "everywhere" for cases where there's less use of a language or less code in general dealing with a particular problem.