Found these discussions in FIND- BRAKE LIGHT SWITCH
may or may not help.
I would look under dash for where it might have been mounted, it maybe missing a ground termination where it was mounted.
My brake switch is mounted on chassis frame just above the brake pedal lever. The plunger is riding on the lever and plunger which is threaded can be adjusted when plunger wears.
The switch controls brake lights, cruise control and the electric steps. The switch is part of the chassis installed by Ford chassis mfg.
The emergency brake light switch should be mounted to frame also.