Another thought...are you seeing air bubbles in the pump basket after the pump has been running for a while? 15 minutes or so. I wonder if you're sucking air from someplace and therefore can't bleed the filter or when you do it just gets trapped air again. Anything in the line between the pump and filter other than a hose or pipe? Also, I wouldn't change the valve setting while under pressure. You said it has Hayward controls and I assume that means a multi-port valve. The danger you run is when you release pressure with the handle the rush of water and/or air can lift the spider gasket off its seat and you'll probably destroy it. The burp out the waste line and all the other things still point to trapped air in the filter. Again, best I can do for now.
Al
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