There are several mechanical reasons for inconsistent results eg is the gantry orthogonal to the bed axis? Is the gantry mechanically sound in regard to travel on each side. If the bearings or the rack is poor on one side then the gantry "walks" as it runs along. ie one side leads then the other side leads or lags etc. This is a sort of slip/stick mechanism. All mechanical components must be checked and found to be correctly operating. My really big question is how are you measuring objects to 1/10000" ? Peter