DE won't backwash off my filter

[studebaker]

Got a new Pentair Quad filter last year. It is a big one which calls for ten cups of DE. After backwashing it has a large amount of DE caked on filter. The window is cloudy for only a few seconds when backwashing. I emptied 30% of my pool last fall doing a backwash and still caked on when I took it apart.

Am I using bad DE? Is my pump not powerful enough? Are my filters screwed up? (I did initially plumb it backward and ran it for a couple of days. Can't see any tears, and it does not put DE back into the pool). Like the crystal clear water. Just hate having to disassemble, and spray off filters.
Any help on this is greatly appreciated.

 

[HermanTX]

How often do you backwash?
I backwash monthly. I try to do a complete filter clean twice a year but this past year just did it once. I have seen some DE remain on the grids when I disassembled (after a backwash) but I think that is just some build up over time. I see it on top of the manifold where there is probably less circulation.