There are a couple of things that could be happening there.
Set Focus allows you to re-aim the camera so it’s directly over where you are placing your design. It bounces a laser off your material and back up getting a very accurate reading. Once you tell the machine to Print it will do a 2nd focus check just to make sure something didn’t change, but sometimes that will fall off the edge of your material which can mess things up (most office folks notice this because the image shifts just before printing).
If your material has a lot of holes in it - or it’s a small piece this is more likely to happen.
If that’s the case you have a few options - creating a jig that’s the same height as your material, covering the holes in the material with a piece of paper, attaching a sticky note to the top of your piece so there’s a larger area that’s the right height… I’m sure there are even more, but the idea is to get a large area that is the correct height for your piece.
You can also manually enter a height into the specific step on the list on the left which will override any auto-focus - but you have to be very sure of your height!
If you want to post a screenshot of your GFUI when you’re seeing the shift we might be able to give more specific help for your particular set-up.