A couple of sextant stories. The first one is folk-law but the second is true as I knew the guy involved;
A flight engineer who had OCD invented a devise using old Hoover pipes to use diff pressure to vacuum clean the flight deck. He fixed one end to the sextant mounting and then opened the flap. Unfortunately the pipe turned inward on itself and disappeared up through the mounting. However it was impossible to release the pipe from the mounting so the pipe flailed around on the upper fuselage for the rest of the flight
One of the navigation instructors had a little party trick. When not on a nav sector he would ask the pupil to leave the flight deck and then do something to the sextant such as remove the bulb, misalign the drums or interrupt the power source. The student would then have to try and sort it out.
Being a fair minded individual, he would then offer the opportunity for the student to do the same to him. After doing this to one student (who has sadly passed away recently) the instructor was unable to get the sextant to work. Whatever he tried, he couldn't see anything. When he gave up the student removed the sextant from the roof. he has drawn over the lens with a chinagraph pencil.
Perhaps beerdrinker can comment on the first story as I've never actually met anyone who witnessed it.