I’m having the same exact issue and it’s indeed Cloud Storage and most probably something in Apple’s network. I am in contact with Firebase support for the second time and asking them if they shouldn’t contact Apple about this, as this has huge impact. Will post if I find out something new.

@ntorring that is an interesting thought, it might be that it's indeed only with specific bucket locations, as otherwise, the impact would be much bigger. I have europe-west1. A Firebase support representative told me that he let the engineering team at Firebase know and they might contact Apple about this. I think they are starting to realize this might be a big issue.