Relyss,
I’m no longer seeing any signs of this bug.
When I loaded my game in dev3116, all the object ghosts which had previously been out on the edge of the map were gone.
No new ghosts were created when I placed items inside buildings (which I gather was one of the things that caused map-edge ghosts), but I didn’t check the item counts.
Thanks. I believe the item count was fixed on 3107, and the ghosts were fixed on different builds too.
I haven’t been able to reproduce this on 3116, so I think this thread could be moved to resolved 
This is not resolved! I just had this bug today which makes me wonder if I’ve had it previously, because I always thought without a doubt my buildings weren’t getting finished because of some other reason. It could have been another reason, or, it could have been what happened today, which is “Placeable items not showing up in the PLACE ITEM menu.”