I've been running my C-beam machine for a little while. I have gotten a few good runs in. There has been some serious learning along the way!! I am having a problem with my Z-axis that I cannot figure out. I have been trying to machine an aluminum fixture that is basically a .5" dia hole .75" depth with an 1/8" slot cut in the side ( making a clamping fixture to hold a .5" piece of round bar.) Anyway, when I run the job it never cuts the whole .75" depth. (I am taking .010" cuts). Then when the tool goes back to w-pos zero it is higher than where I zeroed it. I ran the job again and slightly grabbed the z-axis shaft coupling to feel what it was doing during the run and I can feel it "let go" every once in awhile and I can physically turn it any direction I want like the motor isn't being driven. The same thing occurs when I am routing wood too. I thought maybe I burned out the z-axis driver, so I changed it out and ran the job again with the same result. Any ideas? I am driving Nema23 2.8A 1.79in-oz motor with DRV8825 drivers VREF set at 1 v. I have 1/8 microstepping enabled. I am using BCNC the code is running from the RPi SD card instead of the usb. No other programs running. Thanks in advance for any help.