I created a new Project in Easel Pro using an XCarve machine that is about 4 months old.
I had to cut 20 of these changing the name on the top for each new cut.
I noticed that with each new cut, where I used the Previous location for Work Home, the Z-axis cut deeper each time. Only by a small amount, but after 3 cuts I had to reset the Z location manually before cutting another.
You may want to look at the Calibration for the Z axis steps per mm setting and adjust it if need be. Check out my reply in this thread. Also, check to make sure the connection between the motor shaft and coupling is tight.