Realm Stalling and Resetting Chunks

This started ever since the 1.12 release a while ago. I run my own realm that usually has 10 players on almost all the time. I put a new world onto the realm and now it seems that every time a new player joins, the game will stall. It will stall for about 1-3 minutes and then resume again. But odds are, everybody was killed by mobs or died from fall damage. The game will sometimes stall to the point where it comepletely kicks all players and resets multiple areas of the map.
This includes:
-resetting to normal chunks
-resetting a build area to how it was 20 minutes ago
-deleting random blocks
This is keeping people from joining my realm as well. Sometimes when players attempt to join it will get stuck on loading resources. My realms have never done this before and I could really use some help on this. Thanks.