Don't know anything about this controller I'm afraid has to be honest I feel they are a bit micky mouse so would never use one.!! . . . But the common reason for losing sync with slaved motors will be similar across most controllers so then I'd suggest looking at things like axis Binding first. Then setup regards motor tuning of velocity and Acceleration.
You don't mention any setup details regards speeds etc so hard to tell but the fact this controller uses built in drives and only runs from 24v shows me you will be limited to how fast the machien can run so you may well be just expecting too much from it and have it over tuned.? This is the most common cause of missed steps which is what is causing your racking issue.!