Fox's Mercantile wrote:


Snubbers are the obvious option to try. 0.1uF + 100R in series
absorbs hf content so the gfci doesn't see much of it.


And in case it isn't obvious, that series combination is across
the AC line. Not on the switched side of the load.



** A simple check that a you have snubbed the switch off arc is to monitor the AM band with a radio tuned off station. The noise burst heard via the radio when you press the test button should be much reduced.




...... Phil