Breaking Animation slightly shakes

If you look extremely carefully at the breaking animation of a block, you can see that it shakes just a little bit.

What I expected to happen was...:
For the animation to stay stiff on the block.

What actually happened was...:
The breaking animation shook for every frame of the animation.

Steps to Reproduce:
1. Look directly down on a block
2. Start breaking the block
3. Look very carefully at the animation shaking