[CL] [DU] Missing structure/Floating lots

I have a legacy game that I've been playing for ages, with many families scatted around the game, many in San Myshuno.  I just switched back to a family living in a high rise apartment; to my horror I found that their whole apartment was justt gone!  I got out of that family and went to another high rise to find the same issue!  ALL of the high rise apartments seem to have been DELETED!  I have so many families that are now just standing on vacant lots.  What the devil is happening in my game??!!  I have no mods, no custom content and have never seen anything like this happen before!  Please, if anyone can help me, it would be greatly appreciated.  My whole legacy challenge now seems ruined.