I have a TS2 that recently started lasering out-of-round, non-closed circles. I have checked the belt tension and readjusted the slide rail bearings…with no apparent success. The Y axis continued to run out of round. When I moved the carriage up and down, I could feel a slight jerk.
The solution was: The drag chain of the Y axis is mounted on a small pin. The chain rubs on this pin and brings minimal delays into the system. I have unscrewed the pin. The chain now runs freely and the circles are again 1a round.