Problem z axis - depth bad cut

[Tarry_Brindle]

I would try viewing the troubleshooting videos for potentiometers and stepper calibration here:

X-Carve Maintenance/Troubleshooting Videos - Add Your Own!

There are a lot of repeated questions and answers on here, and some good videos that explain everything. I’ve got 2 maintenance and one X-axis stiffening video that I made that may help with some X-Carve maintenance and troubleshooting. Since a picture is worth a thousand words, videos have got to be worth a few more. If you’ve got a video, or like a video someone else has, put it up on here. Let’s make a collection that will be easy to reference for various X-Carve users!

Since you swapped motors and the problem remains in the z-axis, it sounds more either a power issue or calibration issue.