Sounds like pretty normal results. I have a client that I'm building a house for with almost half the PT 2x's warping beyond usability. We have a stack that's building to return, and I have them keeping me in supply with enough to move forward. We only pick out a few at a time and look for the lightest/dryest ones in the stack.
Once installed, they hold there shape pretty good, but I'm not doing any of those hidden fasteners. I like to use 3 inch screws right thought the boards. The screw countersinks itself and are rock solid.
