Sometimes when a scaffolding block is placed at the corner of another scaffolding block it places two instead of one. And when broken it only drops one out of the two blocks.
If done on a scaffolding block stacked on another block, the bugged scaffolding stays in the air. If another scaffolding block is placed on the bugged scaffolding it stays in the air too, and it has the texture of a normal scaffolding on the ground.
If you exit out of the world and go back in to it the glitched scaffolding has dissapeared.