I know this sounds kinda basic, but have you recalibrated all axis in both Windows and in Aces High calibration routines??
What you're describing is exactly what happens when the stick is out of calibration.
After that you can try a deadband, depending upon how much of a deadband you need, but I would look for the source of the problem rather than the symptomatic fix. It worked once, something changed, now it doesn't work. Find out what changed, instead of trying to cover up the problem, if you know what I mean.
Good luck
Ranger Bob