I would say operator error also. One time I hitched up and forgot to close the front cargo hatch, so I had to unhitch. The handle on my BW would not stay open due to the pressure of the kingpin on the jaws, so I pinned it open. I pulled ahead, closed the hatch and re-connected. I raised the landing gear and pulled ahead a couple inches so that I could remove the wheel chocks. On my way back to the truck I was horrified to see the handle still pinned in the open position! I got away really lucky and won’t make that mistake ever again!