I tried to do some dominoes falling using the physics engine, and it worked OK…then the dominoes went flying everywhere! Here is a link to the VDO. The fun starts about 0:10. I am sorry, I did not save the blend file, but I really did not make any major adjustments to the settings. I did adjust the speed and steps (doubled all defaults) I have Googled and came up with nothing more than “the bullet physics is buggy.” This I can agree with, as many simulations can be severely erratic.
Thoughts?
Steps are here to increase stability of simulation by taking into account moments between frames.
If you double steps, simulation should be more stable. But if you increase speed too, it should be same result as before.
So to increase quality, you have to increase steps and solver iterations only.
You also have to adapt settings to your scene.
Here, dominoes are small pieces. You can enable Split Impulse option.
And you should give them a mass coherent to scene size for dominoes.
If computation is increased by steps, solver iterations and number of dominoes ; you can choose an appropriate Box shape for rigid body collision.
You may also reduce friction.
Thanks. I was thinking it may have to do with colliders. I could not get the box collider to work with the array. It would not keep the shape of the dominoes.
I will try again with your suggestions. So, by increasing the speed by the same factor, cancels out the steps and solver?
Add a puff of smoke where the dominos fly off and call it a success 
As is, it is f*cking hilarious.
Yes. Basically, you end up with same number of steps per second.
Solver iterations are supposed to improve quality of each step. But if problem is caused by gap between steps, it does not help.