Anything that has any form of transparency from plants like leaves, cave roots, and mushrooms, or stuff like slime blocks, etc, have issues with either white backgrounds or X-Ray because they don't have the correct render type

Someone else has pointed out most of these here:
#1867 - Crystal sheets are completely opaque
#1866 - You can see through the ground when looking at glowshroom blocks on the ground
#1865 - yeah the glowshrooms dont work
#1864 - You can see through leaf carpets
#1862 - Colored Slime Blocks are completely opaque