UE5.8 Substrate Toon BSDF Black Stripes Bug?

Summary

I use UE5.8 released version. This issue only occur at the edge of shadow behind a big wall. if the wall is small this won’t happen. If you go into the shadow the deep black stripes will disappear.

What Type of Bug are you experiencing?

Gameplay

Steps to Reproduce

1.create a material and use Sustrate Toon BSDF
2.Create a toonprofile as standard
3.Apply the material to a model for example a sphere.
4.Move it to the shadow edge of a big wall. I scaled the Plane to 20 times big.
I uploaded all I should give you I think. These pictures show the issue clearly.
5.After all have done. the issue will appear I think.

Expected Result

No deep black stribes should appear. Shadow should be always the color I gaved in toonprofile

Observed Result

Deep black stribes show at the edge of shadow, when you move object into the shadow.

Affects Versions

5.8

Platform(s)

Windows

Upload an image

Additional Notes

Thank you if anyone could tell me how to fix this?