I have a problem with brake lights that stay on while driving and won't shut off when I'm done.?

This is a 1986 Corvette. Sometimes the brake lights come on by themselves 5-10 minutes after I have parked the vehicle resulting in a dead battery. I've figured out that the problem has something to do with the master cylinder. I give it a smack on the end with a screwdriver and the lights go out, but if you wiggle the master cylinder slightly the lights come back on. I had my mechanic replace the power booster about 3 months ago but only noticed the light problem about 2 weeks ago. I don't drive the vehicle much at all but it makes me wonder if this is related to those repairs or if it is a separate problem. The reason that I think this is that I noticed that the electrical connector/warning switch on the master cylinder was loose. If that was done wrong, maybe there were other things done wrong. I tightened it and it seemed to make the problem go away but now the problem is back. What is happening here and is there a simple solution?