I rarely if ever encounter bugs that type checking would have fixed. Most common types of bugs for me are things like forgetting that two different code paths access a specific type of database record and when they do both need to do something special to keep data cohesive. Or things like concurrency. Or worst of all things like fragile subprocesses (ffmpeg does not like being controlled by a supervisor process). I think all in all I have encountered about a dozen bugs in Python that were due to wrong types over the past 17 years of writing code in this language. Maybe slightly more than that in JS. The reason I would switch is performance.