Actualy although the Sassan bug is time related it is only the time it takes to do that quest to completion, and you cannot leave to do anything else. You can't go back to broken valley, or leave Sassan to go do other quests on Sentinel island, It has to be the last quest you do on the island before killing Laiken. I have found two more such crash instances on Stones fortress, and am currently replaying that without leaving the fortress, as the game crashes in Stones passage, and also if you try to destroy the generator which produces the armour warrior things after you fight Stone the first time. I hope it works for these as well as it did for the Sassan bug.
