Sure Andrei, I have this feeling that the problem is a poor earth connection outside the house. If you get a voltage on the earth wire when it rains, then that would give you a 'tingle'. Putting an earth rod in would sort that out I am sure, but whether it should be connected to your supply earth in your case is something I would take advice on as there may be a problem with leakage currents.

I have a feeling that this earthing problem is the root of the strange behavior of your CNC machine as instead of putting an electromagnetic calm around your equipment, it would be doing just the opposite.

I appreciate the legacy of communism will be slow to remove, but at least progress is being made.