I haven't done much of anything with this stupid machine but today I had enough energy to try and engrave some wood for a friend. So far the Z axis has ruined the first 2 nice pieces of wood because the Z axis just randomly stalls and loses position, usually driving the cutter way too deep. When jogging the Z up and down it is fine and smooth 90% of the time then suddenly it doesn't move even though the motor is whining, like it's stuck. It happens going up and going down and seems to be random. I played with the acceleration setting ranging from 50 to 10 and it doesn't seem to matter. What can I do to troubleshoot this problem and fix it. I am so beyond sick of this worthless machine.