If you're having multiple unrelated issues, it'd help a lot if you opened a separate issue for each one. That makes it easier to triage and track what needs to be fixed.
Usually when the app encounters an error it can't recover from, it shows a "blue screen" with the error message. Can you please share the messages you are seeing?
Crashing again and again. Unable to signin. The navigations is simply worst and not accoeding to fluent UI