Was there any kind of divider between the tail/brake/backup light housings and the rest of the trunk area? Seems every time I go for a ride on a windy, hilly road whatever I have in the trunk slides around and pushes out the light sockets. Yesterday the soft cooler with the six pack in it took out all three right hand light sockets and lodged itself partially in their place. Good thing there was only two of us in the car, that was a beer each per socket. Amazing how long it takes two adults to push in a light socket.
Over the 48 years with mine I would occasionally have a bulb fall out of the housing. Most of the time I had a light out, it was that, rather than a burned out bulb. When I would pack the trunk to capacity for a vacation, I would always be careful how I pushed stuff down in that area.