Beginner question- spindle will sometimes move straight through stock material

Hi all, we’ve been having a problem where the spindle will sometimes move straight through stock material instead of retracting above it when moving to another part of the stock. This causes the spindle to freeze, and the machine stops responding to any XYZ moves unless Linux is turned off and on again. A tech is going to come and look at this with me, but if anyone has experienced this issue and can point to where to look for the problem, that would be helpful. If you have questions let me know. Thank you
 

You need to post the gcode files (to make sure it's not in the gcode)

Could be Z axis stalling - stepper stalling, or coupler slipping.

Sorry I'm away from the studio and not sure what version of LinuxCNC we use. We use a PC. I'm not sure how what hal or ini files are- I use Fusion360, will uploading the .ngc be helpful? I'm just a woodworker so I have no clue about these things but I'm trying to gather some helpful feedback for the tech when he comes to look.
 

Is an .ngc file "gcode"? I've attached here- thank you

 

Also, last time this happened I ran the same file again and it didn't happen the second time.

I would second the "Z axis stalling" guess especially since it fails on an upward move.
You might try reducing the Z axis acceleration by 1/2 and seeing if you still get the error.

pippin88 wrote:

Could be Z axis stalling - stepper stalling, or coupler slipping.
 

x 2
Either your velocities and acceleration are too high and it misses steps when retracting against gravity or the Z axis coupler is slipping.
Either way your z axis is not fully retracting  due to lost steps or mechanical slippage.