Need some help with original fssb axis output jitter problem

[liliyaea]

I have used the very original fssb part(two ad623a amp) for my warthog upgrade with freejoy.After software and hardware installed,I find the x axis output singnal jitter so much (show with the vkb test app as below),however the y axis works just fine.I have no ideal how to deal with this problem,so need some help,thanks a lot!