did all of the trouble-keys start doing this at the exact same time? or was it gradual, first one, then another...etc. the sometimes they work sometimes they don't suggests something under the keycap preventing it from being pressed properly... something that can move... like a crumb or sand...

did anyone eat crackers, cookies, a sandwich etc.... at the computer recently, or does anyone have a habit of doing that?

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i'd try compressed air. it comes in a can like WD40 with the skinny straw to spray around the 'offending' keys. you should be able to get it in a store that sells computers, or computer accessories... just ask.

many of the keytops snap on and off at least partially also, but i don't recommend you try that unless you can tell what you're doing - the risk is the keytop will never sit back in place properly again.

~ waves ~