Unless Ben's test reveals a hole in your filter, that is clearly not the source of your problem. While I am not a cart fan, if it is correctly sized and functioning correctly, it should filter superbly...I am not up on the sizing of carts vs your 1 HP full-rated pump.

Here is another easy test. The simplest and oldest cleaning system is an old-fashioned vacuum that you plug into the skimmer. If you can vacuum the pool clean with that,nthen the problem is in your cleaning system not your filter system. Then your choices will be to attempt to fix the built in cleaner or abandon it for an alternative.

Carl