Ever since the latest update, this never occurred. 

It all started with my friends exploring out more than we get the "You have been Disconnected" which wasn't the worst until we found out not just my progress was gone but so was everyone (Even those not on the realm). This continued when going to that same area no matter creative or survival.

I thought it was something with items but it isn't or was a certain player but none of which is the problem. The bug occurs when a player is in the said chunk then as soon as they enter that chunk or its loaded, the game crashes and revert to the last save (sort of).