With glass scales it usually helps a lot to have some feedback from the motor shaft (tach).
Do you have the AMC amplifier in velocity mode?
You will likely need some D gain to help stabillize the system.
Post some screen shots so we can see your settings and the response you are getting.
You can use Alt-PrintScreen to copy a Window to the clipboard. Then paste into something like Paint and save to a .png file.
We need to see the Step Response, Filter, and Config/Flash Screens to see all your settings.
Regards
TK