So, a creepy and bizarre twist in the tale happened to finally end the "faulty power button" episode today. Just a few minutes back the side panel glass burst into a hundred pieces in my hands as I took it off to look inside the PC. The power button started working fine since this morning and is back to working normally but I am left with a completely open side panel exposed to dust and all other elements. So, in the end, I will have to go for a new cabinet pretty soon, I suppose. The very thing that I was trying to avoid.

The external button from Amazon had also arrived but it is going back now as there is no need.
P.S. After the comments here, I checked and the power button of the cabinet had the wires soldered on. So, internal replacement of the switch was out of question. Recommendations for a sexy looking cabinet

under 8K (perhaps a fish tank style one) are welcome.