[codefox1]

Usually it is gunk, kitchen fat, or insect/rodent/spider/mouse evdence if no other physical damage is apparent. Got to be careful with plastic or whatever buttons, but if you can get it apart and take a few pictures, you can get some better advice from those of us who have been there before. Some areas of these switches need to be cleaned out and re-oiled, others need to be deoxified or retentioned, but all operations must be done slowly and carefully with appropriate materials. Don't buy a can of contact cleaner and blast it all about if you really don't care if it goes in the dust bin tomorow.

I many times blow or brush all debris out of the way, fix all electrical problems, use a tiny bit of lithium grease and WD40 appplied carefully with a toothpick after small spraying with Deoxit-5, blot everything off with a few Qtips, let it all set to dry overnight, and then proceed. 125 more variations available online.