Give the paddle wheel a spin. Is it smooth? If not, replace the bearings and while you are at it replace all the bearings (8) in all the wheels since new wheels don't come with bearings.
It really doesn't take much to stop the paddle wheel, that's why it is protected under a cover inside the cleaner head. The whole thing is run by the leverage of a small gear against a larger one, the inside of those wheels, but a twig stuck between the small and large wheel will stop it. Yes, they wear out. If you run your Polaris the suggested amount of time in a pool, it will travel over 2500 miles per year according to the factory. They are only a small amount of stainless steel and a lot of plastic.
The biggest reason that inside of the wheels wear is that the drive axle is also worn, look at it and you should be able to see that. The wheels are adjustable on the inside to set the engagement of the axle to the wheel to compensate for the wear which no one, including me ever really does.
If the drive axle is very worn, you should replace it as well or it will wear the new wheels faster.
The easiest way to even out the wear is to rotate the wheels on occasion, they are all the same and it takes about 15 minutes. The rear wheel that is driven by the small center wheel is always going to be less worn. Swapping the two gear-driven wheels from side-to-side evens the wear on the teeth.
I have been using the ATIE brand of replacement parts, on Amazon, with good success. You can get a complete rebuild kit for about $200.00.