I have a couple of DAS Keyboard mechanical keyboards. They're seven years old and have been used daily since I purchased them, one at home and one at various workplaces. They're kinda loud, even the "silent" model, but much better for typing on that the horrible keyboards that come with most computers.

A couple of keys were starting to fail, I had to hit them really hard to get anything out of them. I saw a tip to use CRC Precision CO Contact Cleaner, which is inert and doesn't hurt plastics and can dislodge things inside the key mechanism. I figured I'd give it a go, since the keyboard was pretty useless otherwise. It cost about $18 at miter ten.

I took most of the keys off, gave it a good squirt including using the tube on the problem keys. The liquid ran out of it for a while, so I left it in the sun for an hour then on a window sill for another four hours.

Happily, I can report that all keys seem to be working well again :)