I have set up the OPENBUILDS ACRO 1510 and controlling it via an Arduino Mega board. The two long rails each have a motor mounted on the ends of the short rail just like the instructions describe. I have tried having each motor controlled by its own stepper motor control and also have tried both motors controlled by a single stepper motor control. One of the motors is intentionally wired backwards so it will travel in same direction as other motor. This works with either setup and did not help my issue. The problem I am having is keeping them in sync. I have first measured the distance from each motor to the end of the rig making sure it is equal and square. After moving the rail back and forth a few times with the Arduino they end up different distances, in other words, racked. I have made sure gears and belts are tight. Since using one stepper motor control to control both ( I feel that should be the most accurate) I assume they are both getting the same amounts of steps and amperage. Any suggestions what might be happening?