Soo… fast forward 2 months, have you found a fix to this problem using CM?
I was troubleshooting for about the past 2 hours both googling and changing my grbl settings one by one, with resetting them to “stock” Shapeoko 3 XL settings using grbl 1.1 / build 410, until I finally found (ironically) back to this thread on google. I was so excited when someone else was reporting the exact same issues I was seeing - only to find it was not yet resolved.
@WillAdams do you think you can help or provide any input?
I have tried the same things @xcaper has been using with changing $132, $20, $21, etc, and cannot get the z axis to pass 3.898" no matter what I do.