Have only tried with existing save. (Atrox, in this case)
Random bits of terrain have appeared in mid-air together with debris, mixed in with existing base structures.
Unplugging base structures and moving them out of the way makes no difference to debris - stays hanging in mid-air. Debris items can be highlighted by the cursor, but they can’t be selected and moved. Tried using tool to remove any embedded terrain - nothing there.
As mentioned, also random chunks of terrain just floating in mid-air. They *can* be removed.