Your supposed to deap clean them every year. Mine is in my shed and so it’s a bit problematic to deep clean. What I do is when the pool gets very full due to rain, I backwash it while I drain the pool out. That way I can backwash for around 5 to 8 minutes. I get a lot of rain usually so I am able to do that quite frequently. 2 minutes is the minimum for a backwash with a 30 second rinse.I’d say take it apart if none of your other measures work. I have a cartridge filter so am not familiar with the level of clean a backwash gives a filter. Will let someone with a similar filter comment.