Thank you for the reply!!
So I tried doing the things suggested and for context the lot I've moved the household into was the 888 Spire Apartments in San Myshuno. I saved all the rooms to my library individually, bulldozed the lot and then started placing the rooms back.
Weirdly I'm still having the saving issue but only when placing the last three rooms. Now these are the ones I started updating the decor in but I still don't understand what could be causing this glitch.
I was just wondering if there is anything else I could try before I maybe try moving them onto a different lot or if that would even work in this case as well?
Do you have CC included in that decor? You might have some CC issues. Try building it with game content only.
No, I did at first and took it out as soon as I started having the problem.
I also noticed that I had their photos on the walls and thought they might be causing issues and took them down.
