This is an old bug actually. Whenever I use KCauldron/Contigo/Uranium server core to host a GT6 sever, the players reported that TileEntities sometimes disappear when placed down. The only way to solve this issue is by using Thermos server core (which i don’t even know why, it just works). However Thermos is in conflict with another mod I added so I cannot even start up the server with Thermos.
I asked for help to many server core developers but they either don’t support 1.7.10 now or just disregard this issue. Therefore I came for assistance from you Greg. @Gregorious