Shading on piston is inconsistent from furnace/dispenser/dropper

The back of the piston and top of the furnace are different, which is likely intentional if inconsistent (would recommend changing the piston model - a modified version may be added soon). However, the shading on each of them is different, which continues on to their side textures - the top of the furnace is more dull, whereas the piston is shinier.