I'm charging from the UMC with a 120v NEMA 5-20 and bought the NEMA 5-20 adapter from Tesla. If I'm having problems, it's going to trip right after plugging in the charger and the charge cycle begins. I would reset the GFCI receptical and usually I only have to reset it once for it to work normally. I replaced my 120v GFCI outlet with the best I could find at Home Depot but still have this problem a few times per week. Day before yesterday though it would continually trip and I could not get it to start charging. I probably tried 15 times and all failed. During the troubleshooting I also tried switching back to the NEMA 5-15 adapter for the UMC with no luck but connecting to a non-GFCI outlet charged with no problem. Now this is puzzling, I got the idea to lower the charging amps on the cars display to the minimum which is 5 AMPS, plugged in the car and it didn't trip. Started charging at 1mi/hr so I ramped up the amps back to 16 amps 6mi/hr (what it is normally) and no problem.