X-Carve Depth issues

I’ve had my xcarve for a few years and all has been fine. Now every carve I do, using multiple different files, the depth of cut is approximately twice what I set it to be. I’ve checked that there are no loose screws, the belts are tight, checked the controller to ensure nothing is loose or incorrectly positioned, sent my files to inventables who have confirmed there are no issues. When i jog it seems correct. The only way to get around it is to stop the carve at about 60% completion and set the depth per pass very low. Has anyone had this issue?

If the design is correct and the step/mm value for Z is also correct then any offset is related to either Z-probe offset or mechanical slippage on either the Z-drive or bit slipping in the collett.

If you set up a carve where it will plunge twice (say you carve a design to 1/4" with depth per pass is 1/8", how will this turn out?
You could test by setting up two rectangles in Easel, where one is smaller than the other, center them over eachother. Set the bigger rectangle to 1/8" and the smaller one to 1/4" depth?

Is the depth different between them 1/8" or if not, what?