sleep impossible in Irenicus' dungeon?

[Lemernis]

My first time trying out Tactics.  In Irenicus dungeon, with improved Ilych installed, I've tried resting about twenty times and I can't seem to do it with spawning Duergar.  I've defeated Ilych and his crew (at least the ones right with him) but the party is badly injured.  I'd rather not use healing potions, as they're obviously a precious resource.  Ideally the party should have their spells to continue.  Is there anywhere in the dungeon to rest safely?  If I continue reloading to attempt resting is there some slim percent chance it will succeed without spawning Duergar?

Edit: I rested right before entering the portal to the 2nd level, and quickly scooted into the portal before the Duergar attacked. So at least the party is now rested and has a fresh supply of spells to finish the dungeon.