@Sozki
A few possibilities.... Did you enlarge any items or use MOO at all in the build? Also, have you used the terrain height tool on the lot at all (this should not cause this, but sometimes can complicate certain build dynamics)? Also, can you post screenshots of the basement when this message occurs and the first floor when this message occurs?
Can you please upload your lot to the gallery so I can test it in my game? Just name it something like 'Basement Test' and let me know your EA Gallery ID also. Then post here so I know it is uploaded. Thanks!
@Sozki No problem! Yes, sometimes the easiest solution when something is misbehaving in the game it to try exiting to the world &/or exiting the game and re-entering the lot and see if the issue remains. I'm so glad it has resolved for you! Yes, if you keep a bookmark or something on this post if you just post again and tag me with @SheriGR I should get a notice and we could pursue it further.
Have fun with your build and happy simming! :eahigh_file:
