I have a 2016 Silverado with the same issues but sometimes it would do it when the weather was dry. I found some very helpful information on this forum and thought I would share what I found where the wires go around the front box mount I found it. It rubbed through one of the wires. And where the rear tab mount is on the driver side I found three chafe wires, including a communication wire. It’s a blue and white twisted pair of wires one of the blue wires out of the pair was corroded and was sometimes making a connection and sometimes not I fixed the wires and so far so good I hope this helps