Bad shadow on my rocks with raytracing

Hi,
I am having trouble with the lighting of my rocks.
The problem appears, when the rocks are being placed as foliage. I do that to get less draw calls.

In the four images you see two rocks.
The left one is placed as an ordinary static mesh.
The right one is placed as foliage.
Both are the same model with the same material. As the camera approaches the models, the foliage rock gets ugly shadows.
There is no displacement and no tesselation happening.

The map uses raytracing shadows.
In the fifth image you see the complete settings of the direct light.

Deleting the post process volume doesn’t help, so it is not an AO or LPV problem.
The problem is in the shadows, switching off the shadows.

Alternatively I have been thinking about merging the actors to get less draw calls.
But each rock has its individual spotmap to simulate dirt and wet spots. So, that would be gone.

I hope, someone has a good idea.
Thanks in advance, Christian

Have you solded your problem?
Maybe this can help:https://answers.unrealengine.com/que…9320/view.html