700E Tail Wag when changing gryo.

What happens mechanically and electronically when you change the gyro gain? The reason I ask is because the tail wag started ONLY after I changed gryo settings. Once I made that change, no setting would stop the wag. I checked the tail. The dealer who built the 700 for me checked the tail but the wag still persists.

So, my thoughts are it's either a bad tail servo (unlikely) or the 3GX.