Few keys gradually stopped working

Hi,

Over last year or so I have noticed that some of my keys were becoming less and less responsive. One day I have lost Fn completely. Later "e" started to cause troubles.

I tried to remove and clean the keys following various guides but it did not change anything. OK, I could live without Fn (plus I use an external keyboard 3/4 of the time), but today my "e" has given up completely. I have decided to open it again. Took it apart, cleaned everything inside out. Then I have noticed one strange thing. The key actually worked fine if you push the silicone thing ("dome", "plunger" - I saw different names). Replaced the key back, nothing changed - almost dead. Then I have decided to try one thing. I have glued together a couple of layers of sticky tape (one-sided), cut a tiny 3mm or so circle out of that and placed it right in the center of the key. I wanted to put a bit more pressure on the silicone plunger. Replaced the key...and it works like new! Hmm....Now I am wonderin what is the next step. Clearly this was a temporary solution. I am thinking about a drop of good glue instead of that "pad" to make it more permanent. Any better suggestions?