Hi I have the same problem, but when i load the pre-endgame save, i still can't access to the stronghold, even older save have this bug. I have to go back at least with acte II saves to see that i can access to the stronghold. I never used the teleport cheat or any other cheat before acte IV.
It seems that it's not the use of this cheat which cause that : I played severals hours after teleporting my party out of the last place, and never had any problem with the stronghold and the access. It appears recently for no reason.
