|If this is on a laptop or netbook, their keyboards are more fragile, and it's very common for your most frequently used keys to not work properly after the keyboard has been used a lot, sooner than that happens with an external keyboard.. |
They are a frequently replaced item, and if your model is not ancient, there are lots of relatively inexpensive new clone keyboards you can buy on the web that will work with your specfic model. However, there are many possible keyboards. You need to get one with the same part number, or if there is a picture in the ad that is specific to the keyboard, a keyboard that looks exactly the same regarding what is on the keys and where they are.
In any case, it's very common for your most frequently used keys to not work properly after the keyboard has been used a lot. In that case, it usually does NOT help to disassemble it and clean it. The problem is probably caused by wear of the contacts under the keys. The keys you had problems with will probably STILL be un-reliable no matter what you do.