99 Limo Lights

We have a 1999 TC 120" Limo. Recently, the tail lights and carriage lights have developed a mind of their own. After running for 15-30 minutes they shut off. Headlamps and brake lamps as well as all interior lamps remain on and have no issues. We've had the car to Ford several times. The headlight switch has been replaced as well as fuses. Any ideas? It's obviously unsafe to drive at night as we never know when they will go out. Thanks in advance for any help.

We have a 1999 TC 120" Limo.
Thanks in advance for any help.

Dereck at lincolnsonline is our Town Car Electrical Wizzard, He's also well versed in 120"