recently arrived home. the skies were graying, so i easily noticed white backup lights
were stuck on (these lights are a pair, located in the "3rd eye" assembly, at rear of
the cab roof, above back window).

first i tried some easier jiggering:
tap the light;
open, shut doors;
startup engine, momentarily put transmission into rear, then shutoff as normal;
temporarily pulled the only fuse labeled "backup lights", which is #6
(hmm, maybe i should have tried temporarily running the lights in emergency flasher
mode)

those 3rd eye lights stayed on, so i pulled the bulbs.

before describing the next event, i need to explain the ceiling light (aka
"courtesy/dome light"):
it's been semi-unpredictable since a long time ago. sometimes it works as intended
(it turns on when either door is open). other times, the lens needs a tap, or a few
taps, to turn on. closing both doors always shutsoff this ceiling light. (more precisely,
the truck uses a time-delay before it shuts off this light)

back to the "story".
then while neatening up (return owner manual into glove box, etc) i had to wiggle the
ceiling light to get it turned on. this is "normal". But, after shutting doors *this* light
wouldn't turn off, so after various jiggering ( :-)  ) i pulled all three bulbs from dome
assembly.

after that, no other lights were stuck on.

other brake lights (including brake light in center of 3rd eye), running lights, turn
signals, etc operate correctly. (though i checked these only after pulling the bulbs
from "stuck" fixtures.)

so... maybe whatever causes ceiling light flakiness has only become slightly
"worse"?

maybe this sounds familiar to someone here? i think the only thing left for me to try is
to unscrew the base of dome lights, to look for wire trouble.

____________________________
other info:
it had been raining a little, but i noted that no water had gone past the "foam" type
gasket of the "third eye" assembly.

the rear license plate lights are set into the bumper and got knocked out (forward)  
long ago. (not much room for a shoe in the bumper recess, so  i wonder how the
lights get smacked.)

the pickup is an "extra cab" (whatever they call this) automatic trans,  2wd, regular
gas, 3 liter v6. a/c. original am/fm/cd. replaced aged battery last year. so far, no
electrical work ever done.  about 80k mi