rendering – Unity – Strange Shadow Render Render

Using Unity 2018.2.14 / 15 Recently I have been working on a small project and I found a very strange problem. It's hard to describe, so here's a picture:

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Originally, I assumed that it could be a problem with my shadow / lighting settings (I think it seems a lot), but I could not find any configuration that had a direct impact on the lines.
To ignore it sadly is not an option and I do not know any solution …

Do you have any idea of ​​what is happening / what can I do to prevent these lines from appearing?

Thanks in advance! 🙂