My brake light switch is slightly out of adjustment. I sometimes have to lift UP a bit on the gearshift lever (up towards Park) to get them to come on...
Is the brake light switch at the bottom of the steering column, near the floorboard / firewall? How can I adjust this?
Your brake light switch is probably worn out and needs to be replaced.
Buy a Motorcraft switch.
The switch is mounted on the brake pedal assembly bracket. Unplug the connector, twist the old switch out of the hole in the bracket, and then install the new switch in the reverse.
Then, to adjust the new switch - pull the brake pedal rearward with your hand, then push the pedal forward. This can be done with the engine off. You may hear one or more clicks if the environment is quiet. This will adjust the new switch to your pedal bracket.
Note - do not depress the switch plunger before installing.