I'm getting the same error on my server log... https://gist.github.com/Endmateria/3d42a8894446fdaf34f89ea43905cfbc This log is from the Forge 14.21.1.2397 release for 1.12. I was getting the same error in 1.11.2 though. I think it started happening around the Forge 1.11.2 13.20.0.2366 release and it's been happening ever since. It happens with no mods installed, not even Mercurius. I tried reinstalling Minecraft, reinstalling Minecraft version jar files, reinstalling Forge, reinstalling Java 1.8.131, reinstalling JRE 8U131, reinstalling the entire server via Forge Win installer on 1.11.2. Then upgraded to 1.12 and am still getting the same error on that server. Also noticed getting the same sound problems while fighting Quark's ghosts in the nether (you hit them and they give off the wrong sound effects in the 1.11.2 version). Been launching the server with this batch file https://gist.github.com/Endmateria/a40c7b63940ebb9e33295a507cc4a7a3