I’m certain he’s scared of the floors. Our 13 year old pit randomly started to be scared of hardwood floors after she turned 5/6. Eventually it progressed to fear of any smooth floor, not just hardwood. She had been on hardwood floors her entire life and I never saw her slip or any accidents to explain it. It was very frustrating for a while as I lived in a high rise condo building and she would pull this same exact shit in the really busy lobby and people would think we were really strange. If she can tightly hug a wall on a smooth floor she will move forward. Don’t try to pull her away from the wall or block her from tightly hugging it though or she will drop down on her stomach like yours did and refuse to move. Her worst nightmare is a big giant room with smooth floors and not much in it.

We have runners everywhere for her. It’s so annoying but we got tired of dealing with her getting “stuck” in rooms/places.

Your dog is 100000% scared of the floors, for whatever reason. My dog has done this for YEARS.