How did this happen?

Depending how they are wired the side turn signals only blink or both blink and come on with brake lights. They are not normally a marker light.

 

Yea ive done that a few times. Tight nearly touching trailer with ferring turns (no choice on some of these tight as hell dump sites) and the line gets snagged then rip goes said line. They are pretty cheap so i always carry spares and spare sockets. Just replace it, shut up, and roll imo. Also id ensure you have enough flex in the hangars. I typically hang them so there is about a finger width between my deck and line and get the longer lines beside. Happens less that way.

 

Must have wrapped around the driveshaft, it doesn't take much. I believe a taped light cord is an OOS. Definitely hooked on something. Could have been too short?

 

Be sure to keep your air/electrical lines up off the catwalk, as high as possible. You don't want to lose them running down the road. DOT sees them hanging too low, could be an issue. Probably got caught during/after a tight turn or backing.

 

Looks like it was too long and rubbed. The noise was probably it catching on a bolt or shackle on the frame while you were jacking it in. You need a spring as well to keep it from rubbing or catching, or get one of EXACTLY the correct length.

When I drove for JB, that was easy; with fixed 5th wheels and all the same model cabs, EVERY truck took the same length!