Bleeding LSPV always seems to work fine, fluid always comes out nicely and is not full of debris. Rears lockup good too. But I will double check it using your method.

There is no debris in the fluid either.

A friend suggested I try napa eclipse brand calipers, he has had good luck with them he said. I think my problem is crappy brake calipers from pepboys/autzone. So far in just putting ones on from them I had one immediately leak from a piston, another one leak from where the caliper body is joined together, and almost all of them have had the same thing-1, maybe 2 pistons out of the 4 fail. Only reason I kept going with it was b/c of the warranty. I can change one by myself in 5 mins by now and just need a helper to bleed it lo.

Maybe the pad dust doesnt mix well with the calipers? Im using hawk lts pads and been happy with them.

I do frequently drive in sandy conditions offroad to go quading, maybe the sands getting into them?

What I think Ill do is replace the rear wheel cyls for the hell of it, get napa calipers, bleed the entire system and make sure everything works.