Ideas
Did you build any residential rentals on penthouse lots ?
The LastException file I posted is a new save where I was able to add a residential rental that I'm trying to finish in San Myshuno on the penthouse lot in the Arts Quarter and the game gets stuck on a loading screen and there is no way to play that save file at all even when loading into the save, I also moved my starter sim into San Myshuno in that save file but it was a normal apartment. I made that save file to try and solve this other game issue regarding San Myshuno, I am also experiencing a blank white map when trying to load into San Myshuno in any other new saves that I start (as long as the starter sim isn't moved into San Myshuno like in the save that doesn't load at all) and in my old saves including old saves with residential rentals that I have been working on in San Myshuno on the same penthouse lot and in many other maps. Those other saves that I haven't posted The LastException files for yet are playable as long as I don't go to the San Myshuno map or the current sim isn't living in San Myshuno. I don't think the residential rentals are causing these issues in my game since it happens if I place them or not. If you would like more of The LastException files from my other new saves with the white map problem let me know, I just didn't want to overwhelm this post with a bunch of them without any explanation. I can also start a brand new save without placing any lots and post the The LastException file I receive after I go to the missing map of San Myshuno if that would be helpful.