The mangrove roots texture z-fights when it's next to non-full blocks. This is easily seen with leaves but can be seen with all of the below blocks. This is also easier to see with the top and bottom of the block rather than the sides with some of the blocks.

Affected blocks:
All Slabs (Sides only)
Honey Block
All Walls
All Carpets (Sides only)
All Fences
All Trapdoors
All Doors
Scaffolding
All Stairs
Slime Block
Composter
Enchanting Table (Sides only)
All Beds (Sides only)
All Anvils
Daylight Sensor (Sides only)
Hopper
All buttons
Lectern
All Hanging Signs (Only affects the bottom when the wooden support is present)
Lever
Farmland (Sides only)
Stonecutter
Campfires
Top Snow
Paintings (Sides only)
Item Frame
End Portal Frame
Extended Piston Arms

Steps to Reproduce:

1. Place a Mangrove Root down.
2. Place any type of leaf down against the Mangrove roots.
3. Look at the side of the Mangrove roots touching the leaves from another direction through the Mangrove roots.
   → You should see the texture clipping between the leaf texture and the root texture; if not try moving around a little or try another side of the roots.