On May 27, 10:46*am, dodger741 wrote:
On May 26, 6:24 pm, wrote:

The microwave has been working normally for almost 5 years, but has
recently started making a buzzing sound on start up.

Sounds like your microwave is the culprit and ready to die. *GFCI
circuits must be fairly sensitive to sense small inbalances in current
in their respective circuit. *If the microwave is injecting
significant EMI back into your house circuit, no telling what could
happen. *You could test this theory if you have some sort of emi
filter you could plug the microwave into between the outlet and oven.
I don't know if a surge protector power strip provides any sort of emi
filtering or if it just protects against over voltage spikes.

You could borrow a neighbors microwave for an hour and put it on the
circuit where your microwave trips the GFI. If both microwaves trip
the GFI, you have a problem unrelated to the microwave and probably
some sort of leakage on the other circuit that makes it more sensitive
to the minor surges that the microwave causes when it switches.