My Leaf loves the high-speed charge of the Juicebox, but the JB is not loving my Leaf right now.

It's the Juicebox 40 (not pro, not lite, not wifi) is giving me fits after 5 months of ownership, according to the tech docs, a repeating beep every second means the internal GFCI test has failed.

Is this a common failure of this awesome charger or is it rare?

EMW is hesitant on even taking it for inspection/repair because I bought it refurbished.