I am running a server on 1.12.2, and I am using a custom modpack. I started having problems yesterday when the server randomly crashed and seemed to corrupt my UUID.dat file (it had been working fine for a couple days before). I restored only my correct UUID.dat  to get back the majority of the things I lost and played for a little while longer. I get on this morning and go to catch a chicken using a lasso, and the server crashes. I restart the server, and it works until I join. After I send any data to the server, it crashes with the same message.

I'm not sure what is causing the error. It seems to have something to do with chunkloading on the server, but I honestly can't tell. I've searched around a little and cant find any similar problems. I've dealt with a few minecraft/bukkit servers before (one or two forge ones). Any help is appreciated!

 

Crash log: https://pastebin.com/rhRUk43N

So I edited my UUID.dat file to move my location around and strange things happened. My waypoints got sent back in time to when I first started playing the server (only the first waypoint I ever added showed up) and the map only had that same area discovered. I flew back over towards my base (the server was working fine for a couple minutes before hand, even while I was logged on). When I loaded the chunk that caused errors, it instantly teleported me to the spot where the server had frozen, then the server froze again. Would this just be a bad chunk? How do I fix it?

So when I load the map up and try to select chunks, they work. But there is a certain chunk that crashes even mcedit... How do I fix this?

Well I fixed it. After spending all day trying to use the new mcedit (2.0), I thought to try the old one (1.whatever) and deleting/repopulating the chunk worked!