Heat & humidity. Hygroscopic food crumbs & other debris have accumulated on the key mechanisms under the key covers. You can try to  dislodge this stuff by gently digging under the keycovers with a soft bristle facial blush brush while at the same time blowing air from canned air or vacuum exhaust. Be careful not to dig too enthusiastically because it can be difficult to re-install a keycover that pops off.

That's because it's basic input output device mainly initialized by the BIOS firmware. You likely have a keyswitch hardware issue, not a firware issue. Go to this KB test site and repeatedly press the problem keys for intermittent behavior. If they sometimes register, even if one out of a 100 strokes, the switches are cruddy. They may not be able to be salvaged. In the laptop I'm using right now, I experienced similar behavior with the up down keys and frequently-used vowel keys. I'd get them sorta working for a few weeks, then I'd really have to bang on them repeatedly. I finally gave up and got a new keyboard.