I dunno. I am not an electrician but I have re-wired a LOT of machines. Afterwards I have never had one needing to have a plug turned over or had a tingly feeling in the foot control or the machine. I am not so sure I believe in "stray voltage". It's my understanding that as long as the wires are in properly, well connected, and well insulated that the electricity travels down the wire safely and wishes to stay there.
Only when a wire is exposed and is touching something metal it shouldn't is when it goes off course.