Hi
It could be the nylon rods. Between the lever and the switch is a small nylon rod, about 4mm dia. X about 5mm long, this gets bunged up with crud and gets more difficult to move, remove both switches, if the light then goes out, it’s either one or both nylon rods stuck!
These are very easy to loose! The hole can be cleaned out with a cotton bud and some cleaner, replace without any grease or lubricant.
Paul