I shut down the mine I inherited (using strongwall), did some concrete work and then reopened in a slightly different spot.
The tile that was the original mine opening is now bugged.
It looks like marble paving but mouse over shows it to be "Cave Floor (flat)". It acts like a normal cave floor. Can be raised, lowered, reinforced, prepared and paved. When reinforced and paved the name changes to the correct name but the visual does not. It never stops looking like marble paving. I have also collapsed it (again) and mined it out (again) and it still looks like marble paving.
No idea what to do as I had not planned on marble floors in my mine so it messes with my whole decor ideas (and my ocd ).
Any help would be appreciated.
Tile is at this location: andistyr.github.io/wu-map/14821/#1249_3373
Just relating that I found a tile like that in an old mine. It's now underwater in a boat tunnel, so I decided to not care about it. I believe it shows the original floorboards, no matter what I do to it.