NO-OX-ID A-Special Electrical Grade Conductive Grease
I know this is not a mod or atty and kind of unusual to mention, but if anyone else is having this issue I highly recommend it.
I was having issues with the slides on a year old Nitecore battery charger. The slides became hard to move and felt rough to the point I was about to get rid of it. I dabbed a small amount of NO-OX-ID on the slides and worked them open a couple of times. Amazing!!, slides are working like they were new again and have maintained the results for well over a month of heavy use. EXCELLENT stuff.