shadow issue - scratches on shadows on Android (Samsung Galaxy Tab S)

Hey there,
I have some problems with shadows from a directional light (forward rendering).
I uploaded a picture of this problem.
This are just standard mobile-shaders (spec + diff) but the same problem appears with the legacy shaders.
I am confused, because the problem only occurs on the Samsung Galaxy SM T800.
I think it´s not about quality settings, there is (for testing) just one enabled:

Pixel Light Count 2

Texture Quality Full Res

Anisotropic Textures Disabled

Anti Aliasing Disabled

Hard Shadows Only - High Resolution - Stable Fit

Shadow Distance 70 - No Cascades

Hope someone could help me or has a solution. Maybe it is about the qualcomm Snapdragon 800 chip???
Thanks in advance

I was seeing something similar but not as bad. I set my bias to .25 on the light (was 0) and that fixed it for me on Samsung Galaxy Note 4.

This thread

helped and had similar problem.