I'm using Xtool M1 with current firmware and current design software tool.

I have a simple image engraved onto a cork disk (3") coaster.  To simplify setup I enclosed the image in a 3" circle which I do not output but it makes setup easy.

I used the rectangular grid (4x3) tool to engrave 12 at a time.

To make setup easy I taped a cardboard sheet onto the bottom of the unit and cut only the circle at low power and high speed.  This neatly provided 12 circles so I could position the coasters easily.  Viewed on the monitor the enclosing circles on the design precisely matched the scored circles on the cardboard.

I then put a roughly ¼" thick cork disk and reset the thickness using the auto feature.

The enclosing circles no longer match the reference cardboard.  The design has gotten slightly larger AND shifted.

(1) Why did changing the thickness alter the design?

(2) Is there a way to prevent this in the future?

Thanks for the help.