What I expected to happen: The blocks simply have a hitbox, top and bottom.
Steps for this bug: Pretty easy.
Select, for example, 4-1-3 and place it in the air.

Then, place the same block (for example) 2 blocks under it.

If you now place a block between it (different direction to see the bug), and the block is totally glitched ._.

Nice thought for blocks like 5-1-1 tho