Impala trunk randomly opens
 

My 2017 Impala trunk opens when the car is started by remote or if I'm in the car using the start button.
It's not the fob as that has been ruled out. It's been at the dealer for almost a week and they can't figure it out.
The tech even said turning on the lights will open the trunk.
It's out of warranty from exceding milage and I was hoping to hear some options on what it might be to save some dough on the $145 an hour diagnostic fees.
Other than this I love the car.

Only thing I'd suggest is the body control module.

That's what the dealer said. They also said it needed 6 hours of labor just to check it out. They told me they have to pull the dash. Going to check for loose or corroded connections.