I’m with you. This happened to my Plex app on Xbox One (OG) 3-4 times, over the course of 1-2 weeks (mostly in September, probably due to big updates, UNO UI). And yes it is a critical problem and extremely annoying, resetting most if not all settings. However, it hasn’t occurred for me for a little while (last 1-2 weeks). I was hoping it was fixed. Still worrried, though, because I noticed a bunch of the settings are still missing (like automatic log-in for users, most of audio section, etc). So I’m really not sure WTF is going on.
Edit: Jinxed. It happened to me again last night. Perhaps after every update? (2.41 is recent, see Plex for Xbox One for updates.) Forced to “link” to Plex again. Many settings were actually retained, mostly UI was reset (asks what to display after logging in). Fixed: “Automatic sign in” exists again in settings.