For what it's worth - I'm a licensed Electrician with Electronic Technologist training on top (amongst other skills and training), and I certainly know what contamination can do to circuit boards. At one time I was the manager of a Service Engineering Department at General Electric for a couple of years, and my team did installations and AC or DC Drive Systems servicing (including Synchronous Motor, Steam Turbine, and Hydro Electric generation excitation). Primarily it was Industrial - think Pulp and Paper Machines, Refiners, Portside Container Cranes, Mine Hoists, Cement Plants, Ships, etc. I had Engineers, Technologists, Technicians, and Electricians working under me. We had Customers find ways to put "Crud" into drives in many ways causing grounds, ground loops, component, power supply, and card failures all the time. I know my way around electronics and electrical devices including High Voltage. I was a published Author for IEEE, and an active member on Committees for over a decade. So please don't tell me what a ground loop is.