I service a good amount of D.E. filters throughout the season but this one is giving me trouble. Customer has a Hayward D.E. 6020 that had ongoing issues of clogging fast. The water is crystal clear, properly balanced based on TFP recommended levels, and last week I gutted the filter and replaced all the grids. It still has ongoing issues of clogging. It will run great at perfect pressure for 2 hours, then shoots up to over 30 psi and all flow stops. I took it apart and cleaned it again. There are no CCs in the water and no algae. No dirt, nothing. The grids do not hold water for more than a few seconds if I wash it with a hose indicating they are good. I took the filter off its multiport valve and no clogs are visible. If I switch to recirculate, everything is fine. What is going on here? Is it possible my D.E. has turned into a concrete like substance? Is it possible the multiport has something lodged inside it and it clogs the opening overtime while in filter mode? Help!