Hey Frank,
Besides a ball screw that is simply bent a little too much (should be replaced if it makes such errors, write to support@onefinitycnc.com if you cannot find another cause), I could think of point 7) (ball end nut too tight) in this document
I would also check point 4) (coupler). There was a case when a part had become loose and has hindered the rotation of the screw.
Since your machine is new, it is unlikely that it is point 5) (ball screw). However once there occured this mysterious issue. It was solved by the manufacturer replacing the entire rail.