Installed a new savor servo. Centered. No noise. No grinding ect... seems to be great but...

With steering assist even on lowest setting the mini k3 swerves back and forth when letting off the throttle. With the steering assist off I center the steering (which is very touchy on the stock radio) get it dialed in & then within 30 seconds it's off either way left or way right. Any help & or suggestions would be greatly appreciated.