calico, when I jog an access to a point and back and there is a shift, I usually consider that to be backlash.
Do you have reason to believe there is no backlash? If you're running ballscrews with double nuts, perhaps one came loose and backed off the preload.
If you're sure this is not backlash, it could be lost steps due to motor tuning, or it could also be noise.
Those are my thoughts on it.
Best,
BW