Update: Feb 07, 2018.
I had a lengthy post with my experience, but the terms of the apple discussions do not allow me to submit experiences or rants and only submit constructive answers, and it was deleted. Here are my suggestions at diagnosing and attempts at resolution of the problem whenever this happens:
- Make sure the keyboard is covered with a very thin cover that can be bought on Amazon, and do not allow any dust, however small, to enter. I am thinking of wiping the keyboard everyday with a soft cloth (not microfiber because it itself contains, and may leave, dust particles). But be aware that the cover does change the touch-and-feel of typing, especially for touch-typers.
- If the key is broken, gently test by pressing the 4 corners, and by pressing in the center of the key. Usually, you will notice one or more of the pressure points are the ones that don't look right and maybe the cause of the trouble. Please follow Apple's recommended steps as @riceball99 has above to see if it resolves the issue.
- You can also test by repeatedly pressing the key (gently of course) and compare that to the key right next to it. If you notice that the rate is different (e.g. if you pressed the key 20 times repeatedly and fast, but only got 10 letters, while on the other key 20), this generally means that it needs intervention. Please take it to the Apple Genius bar immediately, or call support, and they should be able to help you. Cannot do much more with this type of an issue. My recommendation is to stop using the laptop immediately after you notice the issue first because it may exaggerate the problem causing the root cause to change (manufacturing defect to accidental damage)
If anyone is interested in knowing my experience, the steps I go through for troubleshooting and the steps I take to try and resolve the issue as recommended by Apple, and what I think about Macbooks, (hopefully someone from Media is listening), I am more than happy to help (Not sure how you can reach me since I cannot put any personal emails here).
Rajesh