We had recurring issues with this happening when we only used circular flat filters. We eventually settled on making a “sandwich” out of glass wool with a micron mesh filter on either side.
Basically you install a filter like you normally would, then throw on a second filter plate ring to hold any edges that kick up around the side flat (in case you use filters which are slightly oversized), then we fill the cavity with glass wool, and use another filter plate clip ring (the kind that pinches into place), to hold another mesh filter down on top of the pad.
We never had any issues since.