I had the same issues with my 2014 silverado LT and it was caused by wiring harness damage where it exits the door. Four wires were damaged. The rubber boot showed a small intrusion in the area of the damaged wires. I suspect that the very slow seat belt retention allowed the seat belt latch to get wedged between the front and rear door and and when the front door was closed the latch penetrated the harness. I replaced it myself in about an hour. Watch the youtube on inner door panel removal. I removed the speaker and the window channel on the front side for easier access. $75 for the harness
