I found this bug by accident, but it allows to get chests from nothing by merging.
In my case, I have placed chests in shape like this:
0 0 1
1 1 1
1 1 1
(0 - empty space, 1 - steel chest)
And when I merged it i achieved 3 by 3 chest.
When I destroyed it, i got 9 chests.
So only with 7 chests in inventory I can get 3 by 3 chest.
