(This is a repeat of the problem described in
MCPE-29509, which was closed as resolved.)
When I exit either of the two realms I play in, no matter if I was only in them for a matter of seconds, and try to enter any one of my own five worlds, I start over in my world at spawn and with all my levels and inventory gone. My structures are all still fine; my world is otherwise unchanged.
Per Mega_Spud's instructions from last time, when I log out of the Xbox app and log back in, then try playing, I can enter my worlds and have all my stuff and levels back, and be at the point I'd left before respawning with nothing. But once I enter a realm, I have to log out of the Xbox app and log back in before I can switch over to one of my worlds.