E key only works when pressed in the middle.

So, my E key on this machine is no longer always working when pressed anywhere other than the centre of the key. I think it might be an issue with the key itself as when the key is removed I can press the rubber button multiple times and the key types fine.

I have never diagnosed an issue with a key switch before so what would I look for in trying to resolve this issue. I could order a new key with switch but would like to try fixing this one before I do that.

Can anyone offer any advice?