Might relate to MC-206460.

The bug

Most trapdoors have a neutrally colored set of pixels on the outermost layer. Cherry trapdoors, however, have lighter pixels on two corners and dark pixels on the other two implying directional shading, which is not the case for other trapdoors.

How to fix

Either change the cherry trapdoor shading to get rid of this effect, or redo the other trapdoors to add such shading for consistency with normal doors and the like.