It is not your game that is broken, it is a bug in the mod which I may have overlooked earlier. As you have discovered, the problem is that Aldeth does not have MAGE04.ITM. I removed it because MAGE01-06.ITM are rings that add a spell to the wearer with infinite durations and I consider them cheating. To fix the problem locally, here is what you should do. Talk to Aldeth as you would normally to set the correct globals. After he has gone to the door and disappeared, use CLUAConsole:CreateItem("MAGE04",1) and open the door yourself. If Aldeth is not present on the 2nd floor, use CLUAConsole:CreateCreature("ALDETH") to make sure he is.
-Echon