That is easier said than done; i have tried it without a few specific mods as they are the only ones i suspect could cause this issue. Namely "The Midnight, Nether Portal Fix, and Progressive Bosses". if i remove all the mods i doubt the server will start without a fresh world file. which kind of defeats the purpose of the test. I can try to remove others individually to see if it is in fact a particular mod causing the issue but im not aware of any of them modifying the way a player would teleport to the end. I do know, that recently the way player teleportation to the end is handled has changed; and im wondering if using older versions of forge, before the change to iteleport, and then upgrading your server to the newer version of forge, is causing this issue. Previously this server was running with forge 31.1.37 and was updated to 31.1.46. The end portal was not an issue before but it appears to be now.