Check the randomizer. Take the unit apart and look at the tube. Try pulling on the white piece that goes into the tube. If it is broken, it will move with A LOT of resistence. You may also notice some black streaking inside the tube. Looks like grit has scratched the tube on the inside. Contact Polaris about it and they will send you a new radomizer tube

I had a Polaris 65 and had the same problem. They replaced the tube THREE times. After the third, I didn't use it and sold it on Ebay and got 90 percent of my money back. It did not work for me.

Pressure in the return was too great, even with the pressure adjuster on the Polaris 65 wide open.

I find it easier to vacuum for 10 minutes then using an automatic cleaner.

Good Luck with what ever you decide to do.