When switching to and back from the new material overlay, existing building ghosts move behind the main tile layer (e.g. become hidden by rock). This doesn't seem to happen with other overlays. Ghosts placed after returning from the overlay behave normally. The function of the ghosts doesn't change, only the visuals are hidden.
Steps to Reproduce
1. Place a ghost building over a rock (e.g. plan a ladder through a chunk of stone) 2. Switch to the new Material Overlay 3. Turn off the new Material Overlay 4. Observe newly hidden building ghosts
This issue has not been confirmed by a developer yet.