Well, i deleted my save files and copied back in my backups and tried again.
One side of my building started accepting the ceiling tiles like normal while the other side did not till i ripped some walls and replaced it.
It should be noted i tried to place a corner roof item and it wouldn’t turn around fully 360 until i ripped down a couple of wall pieces and replaced them, then everything worked.
Well for that side of the base, the other side acted like it had no issues at all.
Keep in mind, i did that yesterday as well and it still wouldn’t fix that void area issue not allowing ceiling tiles but allowed everything else, well most everything else.
No clue what is going on, seems to be no rhyme to it that i can zero in on to say it’s my fault so i can correct it.
Both sides of my base are the same design.
As mentioned before, my pyramid in the desert had a similar issue, and it had no triangle-wedges, but it happened when i was placing ramps along the sides, but it would take the stairs, but not the ramps.
If it was foundation issues, it should still have given me issues on my new base even with the backup.
It seems to have self corrected for the time being, but as i said, it’s not the first time i have had pieces not set.