ProStar PRS4 with FlashCut controller Dual Y Stepper issue

I'm trying to assist a friend who is running a ProStar PRS4 with a FlashCut controller running v7.0.6.26. It has a dual Y configuration with MP-3403 steppers. When jogging the Y axis, the Y steppers are moving at different rates, causing the gantry to bind. It is configured as shown in the manual. The Y motors are defined, and use sub axis 1 & 2. Any idea what could cause the different speeds?

Thanks much

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