All entity model textures are aligned in a specific order, and the front, side and back textures are always rightside up. In the chest texture the front, side and back sides are flipped upside down.

Also the entity/chest/chest_right.png texture changes the left side of a double chest and the entity/chest/chest_left.png texture changes the right side of the chest.

It is painful to update the texture from the old format and there is no reason for this.