When object cast shadow black stripes appear


if I turn on “Cast Shadow” on my placeable actor (will be spawned and placed in runtime), then this strange thing happens

Why is this? When I turn off Cast Shadow, then the material color appears.

I have this problem as well, can’t figure out why.

I think I found the solution, when I move the object on the Z axis up a little bit, the stripes disappear. The object is to close to the landscape.