Hey all... haven't posted in forever. Need a little pointing in the right direction.

My 86 T/A has the high mount stop light on the hatch. A while back, it'd stopped working and I narrowed it down to the contactor in the hatch lid. Replaced both sides of it, and all was right with the world.
Fast forward to current times, and the third brake light is no longer working. I started with replacing bulbs, and when that didn't work I busted out the old volt meter. Popped the cover off the light and verified 12V at each of the four sockets when the brake is applied. Cleaned the terminals and repositioned the bulbs. Still nothing. Even swapped out bulbs thinking maybe I got a bad batch. By application I'm coming up with a 906 bulb, and I know 906 and 921 are interchangeable. Tried both with no success.

Suspecting that at least one socket is just bad and it's killing the whole thing.

These lights are pretty hard to come by. I found one on the 'bay but before I offer my first born in trade, I wanted to see what y'all thought.

Probably not a bad socket. Could be, in some alternate universe; not likely in this one.

Check the 4 sockets when the other 3 bulbs are there. I'm betting you won't find juice.

Reason being, a VERY POOR connection can still pass enough current to satisfy a voltmeter, while looking like a disconnection to the level of current a light bulb needs.

I'd suspect the contacts connecting the hatch lid with the car.