1993 Mercury Cougar Xr-7 Turn Signal Switch Issues And Brake Light Issues

We have a 1993 Cougar XR-7 that is having turn signal and brake light issues. They keep going on and off while driving. We've taken it to a repair shop and they just keep replacing parts at random and not solving the problem. Sometimes they work and sometimes they don't. We've replaced the side signal switch and still have the same problem. I'm guessing it's a loose wire somewhere that they can't find. They also replaced a thermal switch that was under the dash. I've tried to find a wiring harness to replace the old one and haven't found any yet. I really hope someone can help here! My wife is so upset by this. Thank You in advance for your help!