Server Crash - java.lang.Error

Server has crash after having a lot of problems with keeping up.
This happened 4 times already, included 3 latest crashes.

The last crash log is different, I tried with monsters turned off and that have completely different result.

It's pretty random too, as it has not happened for a really long time and then three times in a row. Even after I turned server settings down. It seems like it starts in a really specific area in the world.