Pitch black shadow on sertain meshes in forward rendering

I have a mesh terrain in my game and when I use forward rendering it receives pitch black shadows while other meshes in the level have no issues.
It does not seem to be the material its shader as I have no issue with this shader in other scenes.
Any idea’s what could cause this?

Turns out that in my other scebes the strength of the shadow for the directional light was adjusted to match shadows.
I am not sure why meshes with this shader are the only ones effected with directional shadow strength.