I have had problems with Galil plugin MP3 ver 4.6. It will not allow me to config a second time, and the DROs do not seem to be related to the servo motor encoders, rather they seem only to change on motion commands from Mach3. For example, sending a MDI command of G31 X1 F30 will change the X-DRO to 1.000 even with power disconnected from the motor, and thus no encoder movement. Manually turning the motor and encoder produces no change in the DROs.
Ver 4.4 of the Galil MP3 plugin seems to work correctly.
I have a copy of ver 4.4 that I will share.