Zombies are dissapearing and teleporting in/out in large numbers. This happens with groups of 10+ or more. We just had 500+ zombies teleport around us in all directions when amassing them with a police siren. Shortly after we lit them all up with a molotov they once again dissapeared. I assumed this has something to do with culling but everything I have read suggests it does not work this way. Literally makes it impossible to explore because they can just teleport around you out of nowhere.
It is not mod related. I just did a test on a new server with no mods at all and the issue was easily reproducible. To reproduce the issue use /createhorde 500. Get all of their attention and walk a short distance. All or many of the zombies will freeze and then shortly after dissapear.
The following is a recording I made of the dissapearing issue taking place.
https://www.youtube.com/watch?v=A5tswYV0V0w
Just as they dissapeared in this clip they will also reappear often times completely surrounding you easily causing your death.
