Polaris 65

I have Polaris 65 that worked for 2 months. The problem is that the cylinder that moves back and forth will not move. The plastic seems to have corroded and the cylinder will not slide in and out with water pressure.
I have an above-ground 33 ft. diameter., deep dish pool. I use Soft- Swim, a non-chlorine chemical system. This is the 5th. replacement Polaris 65 I have purchased. Is there a compound I can use to clean the plastic cylinder. I have tried car wax, various household cleaners, sandpaper, emery paper, soft scrub, and so on. There must be something that I can use to "slick up" the cylinder so it will slide.
I appreciate any advice. I can't afford to be constantly replacing the Polaris 65 every few months.
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