Sticky switches.

[alantf]

Yes, looks like there's something not right, deep in the bowels of the switch. Is there any chance of you getting a cheap replacement for the whole assembly? Usually, in a rocker switch, like hi/lo beam, there'e a sort of flexible leaf spring thingy. If this is the case, it could have got weak with age. Just guessing, but it looks like you'll have to strip it or replace it. Good luck with the checking.