Lot / House is bugged?

Hi everyone, I've been having a few issues since the latest update (occasionally the screen will freeze, but the game continues 'behind' it, I can still hear the sims moving around and doing things but can't see it, and need to force quit).

Anyway, this is about a separate issue that only happened yesterday - when I loaded into my legacy family save file, it seems that their house / the lot itself is bugged? I couldn't move up floors, if I clicked the up arrow the whole game would freeze, and would unfreeze if I clicked down again. This happened in live and build mode. After quitting/repairing/clearing cache, I went to upload the lot to the gallery to try to save it (I'm on gen 11 of this legacy family and they have always lived on this lot, it holds a lot of 'history'), and that's when I saw that there is a big black square over the house on all the gallery images. Afraid it was bugged, I didn't save the house to the gallery, I just grabbed as many family photos as I could and moved the family to a new lot, which so far has been working fine/no freezing etc. There is now also a square over the house on manage worlds.

Do you think this is update related / has anyone seen this before? Should I be concerned? I would rather my legacy family live in 'Mgee Manor' than any other lot. I have an older version of the house (from maybe 2 generations ago) saved to the gallery, should I just bulldoze the one that's currently there and replace it with this older version? Or would it be the lot itself? Or even worse, something wrong with the save file? 

TIA