Is this a 120V outlet? If so, set your car to charge at 8 amps. 12 amps may be triggering a circuit breaker somewhere. Also the Volt will tell you if charging has been interrupted.
There's a solution to this guy leaving his charge cord there all the time. Pick it up and turn it in to parking control as a lost & found item. It's not stolen - you're safeguarding his property by ensuring it's properly secured.Normally I would chalk this up to some sort of occasional charging glitch. But there is an interesting coincidence. Every time this has happened, it's when I've parked in a particular spot that has been "claimed" by an i3 BMW who leaves his charge cord plugged in whenever he leaves to "hold his spot." The policy is first-come first-served, but I have a feeling this individual is tampering with my charge cord because he is upset I'm taking his "personal" space. I'm planning on reporting this to our Operations Dept. But first I want to confirm that this is possible. And not some crazy coincidence.