Bouncy rigid body, although bounciness is 0?

The video didn't play for me, but, in a vertical stack, I don't think that's bouncing. It's just the physics system having trouble. The only solution I've found is to set underneath blocks as kinematic. Then have OnCollisionEnter check speed/direction of a hit to see if the block should turn back on. Can be kind of a mess, depending what you expect to happen.

The problem seems to be that 5 blocks stacked is a ton of math. Imagine the blocks are a little off-center. They will lean, spin and fall over, which will look very nice. Unity doesn't know that your particular blocks are perfectly stacked. So, block A pushes down on B, which pushes that plus it's own weight on C ... until finally block F, on the floor, resists and pushes back up. That gives the odd waves. I've had thin blocks just pop into the middle of the block above them.

An idea I haven't tried is to artificially reduce the mass of higher blocks. Then a mass 1 block pushing down on a mass 5, onto a mass 25 ... won't flex as much. Might also try putting blocks to sleep when another block lands on them, but I'd guess any good smack will just wake them all up.