Did you ever figure out the issue with your EVSE? I'm using a Juicebox Pro 40 with my Model 3, and Juicebox GFI keeps getting tripped. Interestingly, all of these occurrences (so far?) have been while the handle is NOT plugged into the car. I've had the same issue with 3 brand new units, so emotorwerks is now pointing the finger at my charging adapter. Fortunately, I haven't noticed any problems actually charging my vehicle. I will try to visually inspect the Juicebox handle and my charging adapter in closer detail tonight.
What happens if you don't leave the adapter on the handle? Does it still trip the GFI at random when it isn't in use? I wouldn't even think you could trip it while not charging, as AC shouldn't be connected to the cable. (Or maybe it checks while the cable is open circuit?)