I have noticed a lot of crashes with up to 1 hour time rollback on Realms, waves of lag spiking and general instability.
Thought it may have been because our realm is very active with many players that come and go throughout the day.
We weeded out villagers and it didn't do very much.
Switched to peaceful and are currently running a 48hr test to confirm if crashes/lag continues.
So far looks good, but if it is the problem, how to keep so many hostile mobs from respawning in underground areas when players build on the surface?
Open to suggestions, I've used command blocks to control mob spawns in certain areas, but with many players out in the realm on their own projects it seems that the hostile mob spawns could definitely be the root of the problem.