Z Auto touch plate earthing / grounding issue

Hi Guys,

I have just installed a C62 BoB and Smooth Stepper. Everything is working perfectly (after hours of research and learning) but the one thing that has defeated me so far is the Z Auto touch plate. All cables are shielded but what happens is if I touch the Touch Plate with my hand, the digitizer diagnostic light flickers on and off and also the stepper motor does not move smoothly when driving down. When it touches the plate, the Z axis retracts but not to the correct height.

Now, if I don't touch the plate with my hand it works perfectly. Also, if i touch the Touch plate with my hand and also touch the machine with my other hand, it works perfectly.

It sounds to me to be an earthing / grounding issue but i have tried earthing the machine direct to the V- on the power supply and even to the BoB but still doesn't fix it.

I read somewhere else that someone suggested to add a capacitor across the input pin and common, but I am not sure what type or value capacitor to try.

Any suggestions would be appreciated.

Thanks
Dean