Number keys not working (or need to push hard) on Macbook Air 13" 2013

Hi guys,

So I have had this issue for nearly a year now...

My number keys occasionally stop working on my Macbook Air 13" 2013. They then sometimes start working again.

In the past when they are not working, I tend to push the keys extremely hard (even resorting to punching/slamming) and then the key seems to be 'pressed'.

What could possibly be the issue?

I would prefer not to replace the keyboard, as since it starts working for a while occasionally it doesn't seem to be an issue with the keyboard.

I have seen one theory on the forums that it may be due to an inflated battery pressing against the keyboard, however this seem unlikely to me.

Any ideas?

Many thanks in advance.