My family uses a Realms server to play together - there are 4 of us in total and the world size is about 250 MB.  2 of the players log in from a Nintendo Switch, 1 from an ipad and 1 from a pc (I think - he plays very rarely).  

In the last several days the Realm has started inexplicably disconnecting.  Sometimes after 10 minutes, sometimes after 60 minutes.  There's no apparent pattern - we are often in different places when it happened.  At one point I restored the realm from a backup and it appeared fixed, but now it's back to doing it again. I downloaded the world onto my laptop and looked for Pending Ticks using MCCToolChest thinking maybe I had a broken chunk but I'm not finding anything in the areas in which we are playing (the busiest areas).  

EDIT TO ADD: I also downloaded the world and was able to play it just fine on my laptop.  Doesn't appear to be a game crash issue but an issue with the Realms service itself.