Your description and the makers picture sounds and looks like a dual drive rack and pinion mechanism - correct?

You could try swapping the electronic driver modules between the two motor drives for the same axis to see if its a driver issue.

You could try swapping the cables from the electronic driver modules to the motor drives but this might change the direction of motion and this might be ok as a test without changing other settings to correct things.

The above should help isolate if it's an electronic issue.

You could swap the motor assemblies with a lot more effort to help isolate a mechanical problem.

But first and foremost I'd try contacting the Maker via their service web site at https://www.mestekmachinery.com/aftermarket

They may have a few suggestions or even know an exact reason/cause and fix.