I'm having the same issue, but just with my rudder peds. Full CH gear - no problems with joystick or throttle, just the rudder peds keep de-calibrating. I just got a powered USB hub, but it hasn't really helped (although I've only had it for one day). My problem is with both AH and Windows.
When I push either left or right, sometimes it works great, sometimes the on-screen calibration bar is sluggish and might not always go to the end of the spectrum. Then when I center the peds, the bar doesn't always return to center.
I've had times when I've flown for over an hour with them rock-solid, and then other times I have to recalibrate while in flight every 5 minutes. Sometimes it helps to just stomp the peds left and right once or twice to get it back for a while. I've got a couple of things to try, but might have to resort to contacting CH for further help, since it's not just a problem with AH.