Precise Collision Detection

Good Morning, Afternoon, Evening ~ Night

I suppose I can be discovered here, posing questions and all, because I'm currently in the midst of designing a simplistic Hourglass GameObject within Unity.

It's one that'll conceivably rotate about its own axis due to a pre-determined animation sequence, And will have little blocks/spheres falling consistently downwards within it, all through the in-Unity physics engine.

The issue that then arises is that the two Game Objects don't appear to collide as precisely and smoothly as I had originally anticipated. And rather than having the little blocks collide and bounce about inside the Hourglass, they instead just glitch out/fall through and bounce away merrily into the distance.

And so I suppose I'm merely wondering whether there's some form of precise collision detection I can apply to these two differing colliders, so they might be able to interact as originally planned, or whether it's all just a lost cause and is best given up on. So any advice/personal thoughts or cold-hearted insults would be much appreciated.

Many Thanks,