Depth changes with back to back carves

Hi so i’ve been using my x-carve to making little signs and do lettering and i’ve run into a odd problem.
If i’m making signs back to back the lettering will turn out fine on the first carve.
the second i can notice it starts out the right depth then gets more shallow towards the right side.
and a third carve gets worse.
Everything seems to be aligned and flat and level. its just so weird that the first one turns out great then gets progressively worse and as time goes on. like if i carve one a day its fine but if i want to do more i messes up.
any advice would be great or videos for help.

Is the bit sliding up in the spindle, maybe? How certain are you that your stock material is flat? Are you re-homing between each sign, or just relying on a bump stop and that your stock is all the same dimensions?

Wood likes to contort itself as its moisture content changes. If you’re sure your machine is square, trammed, and wasteboard level, I’d look at the wood.

I think Kimberly’s suggestion on the bit sliding up the collett fits the symptoms to a T.

I have had the same problem. It is not the bit slipping. When I go to another carve and back its ok. Just a pain not being able to do more than 1 or 2 at a sitting.