On the realm I've been playing on, whenever I die I the "You died" message and the respawn buttons don't appear. Instead, at the bottom of the screen it says "generating terrain" and the realm crashes entirely. Attempting to rejoin the realm, results in a long loading screen then an "unable to join realm" message.

It only happens with certain players.

Also, a workaround is to revert the realm a backup before the player dies.