Cruise control works intermittently.

A search of my database returned this as the closest match to your symptoms: "The cruise control cuts out when driving." The test procedure says to monitor the system with a scan tool when driving and record several parameters. The results of the test might lead to one of the following being at fault: brake pedal switch, voltage backfeeding from the brake switch to the brake lamps, output shaft speed sensor defective, brake fluid leaking into the brake pressure switch, or a clockspring issue. There is no mention of loose wiring connections. It sounds like your best course to fix the problem would be to take the vehicle to a repair shop equipped with a factory Ford scan tool.