Whenever a user logs out, the Plex server that runs in this user context is closed.
When another user logs in, a Plex server is started with a completely separate configuration.
You can solve this issue only by disabling autostart of Plex server under each user account.
Then start running Plex server as a Windows system service.
That way it is started as soon as the computer is switched on, no matter which user is logged in - even without a user being logged in.
