I needed to exit (Save and Quit) my Realm to check my game version on the main menu screen. When I attempted to re-join the Realm, I got a loading screen, but nothing ever loaded. Eventually I exited to the Switch home screen. I closed the game, and after a few moments, the system told me the game had been closed due to a crash. After that I was able to re-launch the game normally, though this takes a long time (MCPE-107374).