Random z loss during radial machining

Hi all.

I am experiencing random z loss during radial machining operation.

Mach4. Nema34 stoppers. It’s all Avid machine.

Spindle will slam in to workpiece absolutely randomly. It can happen after a few min or 3 or 4 hours. Any ideas on what to look at?

Thanks in advance.

See if you can find a solution here first: Troubleshooting