This all started talking about a marker light being out. Making the shop send a truck out to fix a marker is over the top, IMO. The trailer still had DOT approved reflective tape down the side. If you noticed a clearance light out while on meal would you make them send a truck to fix that?
I wouldn't take a trailer with tail/brake light issues, but a clearace, marker or ID light I would be comfortable calling dispatch and rolling with it. As I mentioned earlier, it seems about half of them fix themselves on our bumpy roads.