So, I finally managed to beat the Queen Sattram fight [the giant spider queen in the NW corner of I think level 4], but afterwards, I can't leave her "lair" area.

Am I missing something? Is it a bug that the south tunnel doesn't open back up to the main sewers? I really don't want to have to do this fight again.

Looks like some kind of refresh error.

After reloading a save following the encounter, I was able to leave normally and the tunnel south to the main sewers was no longer showing as "Obstructed."

FYI, this was on V 1.62