Today i had another problem.
After i rendered the small moon animation there were problematic parts in nearly 100 frames.
They are in different parts of the image mostly.
I tried to manually correct them.
It was tolerable in some places but in the very obvious parts i had to give up.
I tried many different options for a full day. But could not find a real solution at first.
It is probably related to high displacement but i didn't wanted to change the look much.
In the end i found the solution kinda in a brute force approach in that
i used the "360 degree detail (highest)" (was too afraid to loose time ones again and haven't tried "optimal")
option in the "Ray detail region" setting in the render node.
Now i am rendering 200 frames ones again.It looks OK so far.
So if you see something like that and have trouble maybe it helps guys.