The problem is I never reproduced this bug. Maybe frames are just not rendering. :/
Solution: escape - open to LAN - enable cheats - go in the teleporter room and break the iron door (don't forget to switch back in adventure or survival mode)... If you have MCEdit, can you open the map with it and look if there's entities next the emerald block ?
If I find enough time to update the map, I'll try to summon the frames when the player is in the room..