Server disconnecting

Server is disconnecting anyone who tries to open FTB quest, ATM 7 to the sky.

When we open the quests with the keybind saving world screen pops up and the game closes and in server console this message pops up.

[02:10:09] [Server thread/INFO] [minecraft/ServerGamePacketListenerImpl]: MomciloUDL lost connection: Disconnected

[02:10:09] [Server thread/INFO] [minecraft/DedicatedServer]: MomciloUDL left the game

[02:08:49] [Server thread/INFO] [minecraft/ServerGamePacketListenerImpl]: BearGrylls60 lost connection: Disconnected

[02:08:49] [Server thread/INFO] [minecraft/DedicatedServer]: BearGrylls60 left the game