The map light in my 240Z got stuck so that when the switch was pushed in to make it turn on or off it would push in and wouldn't pop back out. This was largely due to the top and bottom of the assembly pushing in on the clear plastic switch cover causing the clear plastic to drag. To cure this I glued in a sawed off ordinary lead pencil to bow out the top and bottom of the assembly reducing the friction on the clear plastic switch. The pencil length that worked well for me was approximately 26/32 of an inch and was epoxied in place when it was working right. I painted the yellow pencil gray to hide it behind the clear plastic better. A small bolt with a series of nuts would likely also work and would be adjustable but use lockwashers if you do this.
I also put a small amount of light machine oil on the switch itself on the white plastic post that sticks out of it and used a pocket knife to scrape smooth the plastic adjacent to the moving end of the clear plastic switch to make it more slippery. The plastic seemed to have dirt on it that was causing friction.
Note that the clear plastic switch cover on my car would come out of the white housing on either end once the heater fascia cover was unscrewed for access to the map light.
Bottom View of post location:
After modification before installing in car: