Get a sump!! LOL
Sorry, I know it isn't the answer you want, but I just dread canisters. I had a lot of heartache and issues in my past with them and have pretty much swore it off... Id take some aquaclears any day.
Your filtration should never be smarter than you... canisters just annoy the F out of me, faulty to no end if you ask me...
Is it loosing pressure or suction somewhere? No kinks, are the seals all good?