How about the motor? This is actually common on older motors that are full of brush dust to have a bit of a ground fault and it is pretty difficult to tell a controller ground fault from a motor ground fault so long as the two are connected.
I find that with a dirty motor and a Curtis 1221B controller I can trip a GFI, and that things don't have to be nearly as dirty when the motor is liberally doused in rainwater.
I find that with a dirty motor and a Curtis 1221B controller I can trip a GFI, and that things don't have to be nearly as dirty when the motor is liberally doused in rainwater.