ToME: the Tales of Maj'Eyal

In the late game, I went back to Maj'Eyal, and the Last Hope farportal just disappeared. I was again able to knock at Tannen door and (spoilerish info removed...). But the Tannen dungeon was empty and at the end the portal did not reappear.
Not a big problem, indeed, there is still the Reknor portal, but obviously a bug...