My Polaris 280 barely moves at all. It basically sits on its front wheel with its back end up at about a 45 degree angle. I checked the wall filter screen and it is fine. The backup valve is leaking a little water all the time so I ordered a replacement, but it can't be losing enough water to make a difference.
When I turn the front wheel by hand, it is the only wheel that moves, and the sound reminds me of the sound of something stripped. The small center wheel and rear wheel spin freely, and the single wheel on the other side seems to have normal resistance.