Oh man, I used to have that same problem! I found that if I didn't heat the base of my piece as thoroughly as the rest, it would just pop. Now I make way smaller, slower adjustments with my flame and keep it spinning steady for way longer before I even start to shape it. It takes more time but saves so much heartache.

Honestly, I have to push back here, @henry_morgan. I don't think a white noise machine could shake a bookshelf loose. Those things are for sound, not real vibration. It's more likely the shelf was not put together right or the wall is weak. The neighbor texting about drilling just shows how loud it was, but not from shaking. Tbh, this story seems a bit off to me.