I have a 2007 300C HE. While the car is off and all doors closed with the keys out of the ignition, every minute or so I'll hear a clunk in the rear end, followed by dash lights blinking once, followed by the gauges pulling down below zero, then returning to zero. This is draining my battery overnight. New alternator, new battery. Confirmed charging system. I've searched these forums for 1.5 weeks, and can't find anyone with issue.