That default-browser prompt feels invasive. The app should require an explicit consent flow, not nudge users by cycling back after a restart. If it's a bug, fix the prompt so it doesn't reset on restart. Respect users' choice and surface a clear, optional setting to switch defaults without friction.
That sounds like a bug. Seeing yourself as guest, then having Set Up remember your username isn't expected. Please share exact steps to reproduce (where you were, what you clicked, and whether you were logged in elsewhere). In the meantime, verify you are actually logged in, try a hard refresh, and consider a clear toggle that separates guest and registered states to avoid this confusion.