Mystery Issue- vehicle shuts off in Reverse

[Tmiller1]

I bought my 2012 Equinox brand new. Within the first year I had to replace my first battery. My vehicle is now only at 75,000 km and I have replaced the battery 7 times. Each time my car was found dead with a dead battery ( winter or summer) after being parked for the night.Load tests were done( no draw found)the command start was removed, a trickle charger was installed, and spark plugs and solenoid’s were changed each time. Sadly the mechanics were unable to find a reason for this. As for driving it is kept in a heated shop- plugged in for the winter, and driven daily with a minimum hour long drive once a week to try and maintain battery life. In the last two years the vehicle has been shuddering while idle and losing power. When I put the car in reverse it shakes till it shuts off. No dash lights or warnings come up when it happens and it starts right back up. It has been scanned and the code scanner comes back empty. I have paid $1200 this month between two shops for investigation and they cant find anything. Do you have any idea what could be happening? Have you heard of any similar issues? I just really need some direction on what could be causing this unknown issue.