I've had a VLine2 in my 2011 G37 for over a year now, and have always had issues with the unit not starting when the car is started. It manifests itself quite differently at times. I will try to explain.
One scenario, during Arizona summers of 110-130 degrees (in-car), the deck often does not start. If it was on the ipod interface, it'll just error, and never switch displays. Flip back to radio for the drive as it's all I'll get. I'll say the unit was not tested for crazy az summers.
Second scenario, during cooler times in AZ, it usually works to start, but if I stop along the way shortly, for gas, food, etc, often the vline will not take over or shows in error on ipod interface again. This is more common than not sadly.
Third scenario, the vline goes into poop mode, and breaks my car, giving me no video display, no ac control, and essentially no control of anything in the middle of the dash. I have to physically power down the vline, and power it down, I give it 30sec or so, and plug it back in. So far it always comes back to life, but scared me the first time it did this randomly the vline fried my car.
I've always kept it up to date, but this just seems like hardware defect at this point. Curious if anyone else in hot parts of the country have seen the same behavior.
I do have the 8.0 upgrade, but not applied it yet as it's typically quite angry/broken more than not during summer.