HarbingTarbl

That's what I suspected as well, except the issue continues even when all mods are disabled. I suspect that something is writing bad information to the world, but nothing showed up in MCEdit and it only seems to happen on disconnects.

I'm running a modded server and I'm getting an "Illegal State Exception, Entity Already Tracked" whenever a player disconnects from the server. Client side mods are the same as the server side ones, with the exception of Optifine. I'm running the following mods: (This crash continues even after disabling all server side mods) Here is the section from the forge log Here is the normal server.log