[J-(Chicago)]

I'd check the harness in the trunk and see if the connections need cleaning.

You can always check the sockets for power with a voltmeter.

I don't know much about the brake light switches on those cars, but could it be possible that the wrong stop light switch was installed behind the pedal over the years?

When I replaced mine, the auto parts store didn't have a matching one to mine and i had to rig in one from a buick something or other and leave the cruise control terminal unplugged.

if your original stop light switch had 2 different spade terminals for the lights and a 1 spade connector is installed, that could be the issue