Brake light ground issue

About twice a summer, I have a ground issue with my brake lights. I have to remove the tail lights on my 71 Scamp, twist the bulb socket in the housing and reinstall the light. This freshens up the metal and creates a good ground again and everything works great for awhile.

Just removing and tightening the bolts that hold the light to the bumper doesnt fix it. I have to twist the socket in the housing. I've thought about using dielectric grease on the bolts that hold the housing to the bumper, but its more the housing and socket contact. Since there is no ground wire and its using the body as the ground is there a good way to solve this issue permanently?

Besides replacing sockets I have found two ways to fix that friggin annoying issue.
1. drill the housing right where the socket metal meets the housing metal and put a small screw in the hole.
It will make the contact between the two metals.

2. I soldered a ground wire on the edge of my sockets with a ring terminal on the other end to one of the lens mounting screws between the lens and housing.
The lens screw will pinch the ring down on the housing metal, and if yours have the gaskets put the ring under the gasket.
Take the plastic off the terminal and solder it on the wire.

Both work perfect.