If you are using the nemedian set’s foundations and ceilings know that there’s a bug on those two from the set following up that if you are in the brown island down to the right of siptah I heard from some people here on the forums that area is bugged too.
If you aren’t down there and you are using the nemedian set’s foundations and ceilings, I would suggest you to use ceilings and foundations from the non dlc vanilla sets.