FWIW, and WRT infra-red remotes, I used a tiny dab of that rear window defroster repair paint (it's a conductor, of course) on a stereo remote once.
But I had to take it apart to get at that surface. The conductor on the surface does seem to wear with lots of use. (This was on the volume control, which I hit a lot.)
Not worth doing this for a mouse unless you want the technical experience.
It's not impossible for the debounce circuits to not work properly with a poor switch connection, resulting in two coded pulses to be transmitted.
Son2 rinsed a device (cell phone?) in distilled water in an ultrasonic cleaner after it fell in the toilet. "If it doesn't work, you can't break it, right?" he remarked. But he's got bigger balls than I do. He let it dry quite thoroughly for a couple of days, maybe a week, and restored it to service. In general, water doesn't bother electronics if it's clean water and it's dried thoroughly. They wash the things off at the factory, right?
I can assume you tried fresh batteries, yes?
Another thing I found is that the transmitting LED sometimes gets dirty, as well as the receiving area on the receiving gizmo.
Also, make sure there's nothing blocking the line-of-sight IR signal from the mouse to the PC. On my TV remote, my big fat feet on the coffee table sometimes block the IR signal.
Again, all For What It's Worth.
Terry, 230RN