I've never seen it do this before. What you are looking at is the allocated charge amount (the charge rate at which the charger is telling the car it can draw) and the actual amount the car drew. The short spikes to zero are normal. The long dips to 6A are what I've never seen before. It's cold right now but I've seen it charge in much colder temperatures than this (it's about 30F now) without doing this.
Only thing I can think of is the charging unit in the car is limiting the charging current. The only reasons that would happen would be due to the temperature of the battery modules (there's 5 modules, 3 temp sensors in each module) being too cold or too hot. The charge current and battery output are controlled based on the temperatures (and other factors)...I would also agree that is odd for it to kick in...I could see it doing that if it was in the teens. A software/power glitch seems more likely, there is a tail towards the end of charging but that appears to be towards the last 1/3...
