I've witnessed the same issue right now with a user who is unable to uninstall the app due to this issue ... Feedback Assistant ID: FB10567269

Okay - unfortunately for me - I've eliminated the Firebase component by sending the notification directly to APN via the command line (as described here) This worked! Therefore the error must be with the Firebase SDK and my usage of it. Once I find a solution I will post it here for reference. Out of curiosity I would still ask where to file bugs for APN in the future? I couldn't really find a suitable category in the Feedback Assistant?

I'm using token-based authentication - I've created a key on the Apple Developer portal and set this with Firebase and removed the old certificates from Firebase and the Apple Developer Account.