Make sure that the droCurrentX editor property is not still set as read only. This was reported a year ago for the lathe screen set and wasn't changed the last time I downloaded a new version last fall.
Not sure what you are trying to do but I think you probably should be using mc.mcAxisSetPos(inst,mc.X_AXIS,10.3456) rather than changing screen values.
Just my 2 cents worth
HTH
RT