Taillight problem

My 98 T&C passenger-side upper parking light doesn't work. Only the
top bulb, the one below works fine. All bulbs test fine. Brake light
works. If I swap the passenger-side assembly to the drivers-side, the
problem moves to the drivers side, so it's in the assembly.

On the back of the assembly, there's 3 little bulb socket screw plugs
that pop out, each with a bulb attached. They look like they have
part numbers on them -- 8072 and 8072. I'm thinking one kind goes in
certain holes, another in the others, but don't know which.

Anybody know if there's a difference between the bulb sockets? Does a
certain one have to be in a certain position?

Thanks.