How does EMF cause these problems in the first place and would it help to put the Arduino in a lead lined box and to that solder the shielded cable that goes to the Arduino?
Standard industry practice is a soft steel [NEMA enclosure](http://"https://www.automationdirect.com/adc/overview/catalog/enclosures_-z-_subpanels_-z-_thermal_management_-z-_lighting/enclosures?utm_source=msn" cpc&utm_medium="cpc&utm_term=nema" enclosure&utm_campaign="Enclosure&utm_adgroup=Nema" enclosures&msclkid=70b4bf0d69621e14d383e0f37e4c43d2) with the paint wire brushed off with a wire brush drill bit at the mounting location of the machine screw that secures the ring terminal for the Earth
GND. (GRE with Yel stripe) In your case solid green is fine. There is no advantage to lead over soft steel
as any metal will basically block the RF. If you can't afford a NEMA enclosure an aluminum box would
probably work.