Issue #21698: Inverted grass normals on farm stone walls
Not sure how to add images so they appear here, but here's a link:
Ignore the red circles, they are for another bug report.
Afaik, the grass on these wall parts (and i think all of them) have inverted normals. I seem to recall that the normals were once flipped, to fix inversion on the stones. It appears, that a selective inversion is in order, where now the grass has to be flipped, but the stones kept as is. Good luck :D