On Tuesday, July 24, 2018 at 2:01:42 PM UTC-4, wrote:
A power surge when
the magnetic field collapses?

Very likely this. Old-style electric clippers do not use motors per-se (things that spin around). They use what is, effectively, a buzzer that switches the electric field around a magnet pulling it back and forth. When the field collapses, the magnet induces feedback, and will trip some GFCI devices..

https://www.google.com/url?sa=i&sour... 542641709432

Just for giggles, try turning over the plug in the receptacle (unless it is polarized). It may be that the pulse is going down the neutral line and is thereby seen as spurious by the GFCI.

Peter Wieck
Melrose Park, PA