If you mean bug with not being able to log in, when you are switching acc it is with us since last few updates. It is annoying like *heck, and i don't like it also. I suggest to either contact Live Support with that, or make post in [Version 1.7.7] Official Bug Thread - June '2020
If you mean something else you need to specify device model, operating system so tech team can verify this.

Unfortunately sign in for Android is driven by Google+ and sometimes it is just not working, this can be verified by going to Google Sync is using an emulator such as Bluestacks and resyncing the accounts.  Generally after an update you should clear the caches to ensure smoother gaming.  Finally I have found that if you use the link ingame for Live Support and tell  them you are having an issue switching accounts, once they do their backend check, the feature runs smoothly.  Good Luck!