A month ago I couldn’t get my gas cap back on after a fill up and after fiddling for 30 seconds it seated correctly (although I don’t know why). Next fill up it happened again. Yesterday it just wouldn’t seat so I drove home with the filler door open about 2 inches.
Looking at the filler cap in my hand, I saw a spring but couldn’t get it to compress. Saw white nylon housing that seemed secure and unmovable in a depression on opposite sides. See photo.
I got some 3 in 1 oil and gave a couple of drops to each incline and put back in filler neck while pushing down with large pliers and turning clockwise. After 3 times, it closes effortlessly.
Might be a good Preventative Maintenance item to add to your list.