What do you mean by "failing tests", are you talking about runtime code? TypeScript erases all types at compile so these wouldn't affect tests. Unless you meant "compile errors" instead.

I've noticed LLMs just slap on "as any" to solve compile errors in TypeScript code, maybe this is common in the training data. I frequently have to call this out in code review, in many cases it wasn't even a necessary assertion, but it's now turned a variable into "any" which can cause downstream problems or future problems