Great news, hoping for the best for you!
While I had my '3' keycap off I did some playing around and found some very interesting behavior with the plastic key cup. Wasn't sure if anyone else has noticed this so I captured it on video. If I struck the area outside of center, it produced the loud noise (only sounded like this when heated above 50C, at least on my machine). If I hit it direct center, it behaved as expected.
It's hard to see in the video, but my wild guess is somehow the layers of plastic react differently when heated.