被破壊メッシュが置き方によって壊れない現象

I am unsure what you are saying. But if you want the glass to move, u need to check simulate physics. As of what breaks the object exactly, there is a function that you can call that is named “Apply Radius Damage”, you just set the location and the reference to your glass, and the damage amount and spread radius.

Since your mesh is being destroyed on impact, I would recommend looking at this answer that might be more usefull: