I took a look at the debug file. I didn't see any MPG commands in it. It does show that you are using Mach to slave your Galil D axis to your Galil A axis.
The Galil plugin was developed primarily to enable the use of analog servos in Mach. You are using your servos like steppers. That being said, there is support for stepper motors in the Galil. However, support for stepper motors is very lacking in the plugin, as none of the developers of the plugin have any stepper motors. Stepper motors seem to work fine with a basic config. But slaving is not the same command with steppers, as you have discovered.
If you enable slaving in Mach, then the galil plugin is going to send a GA,,,X, as this is the proper thing to do with servos. This basically negates your previous command of GA,,,CA. So... you need to disable slaving in Mach and do it all on the Galil. These commands are what you will be needing in the GalilInit.txt file. Remember, no slaving in Mach!
GA,,,CA // slave axis D to master axis
GR,,,1 // gear ratio 1:1
GM,,,1 // gantry mode
(Leave the comments out of the file.)
This way, Mach only controls axes A, B, and C. The Galil does all of the slaving. But... you will have to make sure that the gantry axis is square before Initializing the Galil from the plugin. When Mach homes the gantry axis, it will think it is only homing 1 axis. Mach will have no notion what so ever that there is a slave configuration. This is fine, as long as you realize that none of the Mach slaving controls will be useful.
I updated the plugin code to take a look at the master axis motor type and do the right thing if it is a stepper motor. However, that will not be available until the next release. (I don't know when that will be at the moment.) Maybe this will get you going until then.
Steve