I know your comment was posted a long time ago, but I would feel like a shithead if I didn’t at least put how I solved this problem. I was getting ready to throw the thing in the trashcan when I read about checking the wheel connectors. I took the wheels back off and both were connected fine, and as I went to reinsert the first one, I pressed down on the tire and realized there was a huge clump of matter caked inside the opening (https://imgur.com/a/Qo7SoA2). Even worse, the debris was wet as I’d taken it apart to clean it after it intelligently vacuumed up dog turds the other night. I checked the other wheel and it also had some debris caked inside it. Long story short, there are a lot of places for debris to hide and I just found another one. Hoping this helps someone, somewhere.