It's a finniky , PIA job but , you can lay out a BIG beach towel and open up the light switch and carefully scrape out the dead bugs and then polish the copper contacts until they shine and then find the tiny ball bearing & spring that fell out onto the blanket you didn't neglect to lay out and re assemble , it'll work like new for another 35 years....

It is not permissible to sand or otherwise abrade the contacts , do so at your peril .