If you look carefully at the Microswitch, there are clips at both end which allow you to open up the casing without damaging the switch.

Inside, there is one piece metal spring with the contact at one end.

Do not remove the spring, it is extremely difficult to replace it.

Look carefully, one end of the spring is the contact point.

Place a piece of paper in between, gently press the spring and then rub with the paper.

After cleaning, can easily last for another year.
Make sure you have good eyesight, a magnifying glass is more costly than a soldering iron.