from a 2 second glance, I fail to see how this could occur unless something on the server induced an illegal world state, vanilla had logic to try to detect such issues last I knew, so, on the surface, all I can guess is to try without plugins, otherwise, we'd need some actual us...
Improve Server Connection Speed:Improves the speed of connecting to servers by setting the InetAddress host name to the IP in situations where it can be represented as the IP address, preventing getHostFromNameService from being to be run Incurable Potions:Excludes potion effects from being curable...