GFCI downstream protection
My treadmill was plugged into a GFCI receptacle, and it tripped the GFCI while I was trying to ramp it up to 12mph. I suspect a noise spike generated by the treadmill's motor or motor drive circuit. I have since changed the treadmill to a standard receptacle.
I have another GFCI in the kitchen that has tripped out a couple of times. I have been watching the situation, and checked all connections. Maybe a "nuisance" trip, but perhaps a problem with one of the appliances connected to it.
IMO, GFCI's are susceptible to spikes on the line which are not related to stray currents.
It's the nature of the beast, but a very small price to pay for the protection.