When the probe touches, the digitise input is on, so that's fine. The only thing I don't like in that screenshot is their spelling of digitise!
The fact you get different results each time the tool touches implies you might have a problem with interference. How is the probe connected and are you using shielded cable?

Also, U notice you have the kernel frequency set to 35kHz. Are you sure it needs to be that high, as Mach3 is likely to be more stable if you run it on 25kHz. I doubt that's causing any problems with the probe.