Hi Dave
You may have mentioned it somewhere, but I haven't found it.
What version of Mach3 are you using, and are you using an ESS? If so, what firmware version for the ESS?
The reason I ask is that I KNOW, from personal experience, that some versions did not handle probing properly. Strange values got returned in the 200n variables at times, and other oddities. A few 'bumps' were experienced.
However, having updated to .062 and ESS u4f1a (weird, but I think that's right) I can now do probing with sub-micron resolution for thousands of cycles on end. I am even game to walk away while it is running!
Cheers
Roger