Bug: Lv3 Alchemy Room shows no transfer socket after killing all monsters

I've killed all could be killed even next room's monster at the door.

I've run this several times, everytime when I finished all monsters in this room but with no sign, I'll go to the door to kill some monsters next room close to thje door then I can get the transfer socket.

But I got no luck this time and I remembered I've got this once before, only thing to do is to close the temple, lucky I have locks.

Please fix this bug!