Bill
Just a shot in the dark. Looks like BOBCAD code. I had this happen to me a while ago.
When aligning the stock using the stock wizard, somehow an offset was applied.
As it is only .020 it might not be noticeable on the screen.
I realize that if this is happening consistently, the above is unlikely. See Below.
As an aside your backlash should be sub .001. Sounds like some adjustments are in order.
I would check the X ball screw nut tightness and the X gibb adjustment.
Both are relatively easy to reach and do not require any dis-assembly.
Good luck
John