It is not related to any particular map or mob. Game simply can't handle inner demons (or similar skills) at madness difficulty.
West is basically ok. Odds of crash are low. When you go to east (mobs 70+ level, lot of abilities, spells, items etc) problems with saves become a SERIOUS issue. You never know when game state is too big to be serialized. When you cast inner demons on wrong mob you can basically kill tome process because you won't be able to save game, go to main manu, leave level etc. Even "Exit Game" option won't work
When you try to save game, ui will be frozen for a few seconds and then game resumes like nothing happened. No information in logs, no information in game about saving game, nothing.