I've had a realm since about the start of December now, and I've only had some minor problems, until now. This has happened >3 times now. Me and my friends will log onto the realm, and start playing. Then, anywhere from 1 hour to 3 hours later, the realm will randomly disconnect you (bring you to the dirt screen that says "Disconnected from server"), and when you try to rejoin, everything is rolled back to exactly the moment of when you first joined the server.

I've encountered this glitch firsthand on my Windows 10 PC, both the client and realm on 1.16.201, but my friends have encountered this on Xbox and mobile as well. It seems to be a server-sided problem.