Go to to C:\Users*Usernamehere*\AppData\Roaming.minecraft\resourcepacks\Faithful32-1.12.2-master\assets\biomesoplenty\textures\blocks. Copy the 3 dirt textures loamy, sandy and silty to desktop. Rename them to grass_loamy_side, grass_sandy_side, grass_silty_side then copy them back to ^ that directory replace the broken textures and your done. :)

Go to to C:\Users*Usernamehere*\AppData\Roaming.minecraft\resourcepacks\Faithful32-1.12.2-master\assets\biomesoplenty\textures\blocks. Copy the 3 dirt textures loamy, sandy and silty to desktop. Rename them to grass_loamy_side, grass_sandy_side, grass_silty_side then copy them back to ^ that directory replace the broken textures and your done. :)

FIXED TEXTURES HERE

Chances are that this leads to flickering for OpenGL renderers. I will have a look at it in a couple of hours and merge / adapt your fix.

I just checked, and the grass textures are identical to the Vanilla 'grass_top' and 'grass_side_overlay' textures.
(Or at least the textures in 'TODO' are the same as vanilla)
Therefore, the textures should be copied from the vanilla faithful pack.
I think this would also fix the issue

Chances are that this leads to flickering for OpenGL renderers. I will have a look at it in a couple of hours and merge / adapt your fix.

Just realised that the grass texture is a lower res to the rest of faithful there is your real bug