Photo and description of workaround
I still have the tail light/marker light issue from time to time. My homemade device still does the trick when I need it. Photo is posted here.
Go to the nearest auto parts store and buy a male RV trailer connector, 12v test lamp, and an inline fuse holder. A 10 amp fuse should be sufficient. All of this should cost less than twenty bucks. Using the test lamp and the diagram that comes with the RV connector, find the pin that is constantly powered. Using leads on the fuse holder, connect this pin to the tail/marker light pin.
Now when you plug this contraption into the socket, the tail/marker lights should illuminate. Just remember to unplug it when you reach your destination.
All of this assumes that your problem is the same as mine.