I had he same issue on my '86 Spider Graduate. This is how i repaired the hird brake light: Removed the nylon socketAlso. When you experience those 3 tag lights don’t work, and they didn’t work when prev. Owner had the car. I found after pulling out my hair out, that the power switch got installed backwards by prev. Guys trying to fix them. Turned it around and worked.
assembly; cut both wires; bought AutoZone part # 85804-Universal Single contact socket for #1156 bulb; removed center lead & spring, drilled hole in socket for hot wire to pass through & larger hole for ground wire to pass, then crimped butt
joint onto wires & re-inserted nylon assembly: it now works! Chief Bre