Why do I get this weird shadow render error?

Question

Using Unity 2018.2.14/15 I've recently been working on a small project and I encountered a very weird problem. It's hard to describe so here is a picture:

Originally I assumed it may be an issue with my shadow/lighting settings (I think it looks like that a lot), but I couldn't find any setting that had a direct impact on the lines.

Ignoring it sadly isn't an option and I don't know of any workaround...

Some additional information:

1. The problems are 2-3 well visible decreases in lighting brightness. It seems a bit like there is something causing automatically descending lighting quality the further away from the camera the walls are, however I haven't found a setting to change this yet.
2. Currently I'm using quads and a custom material based on the Standard Opaque Shader with an Albedo setup. I'm using a self-made Texture for the walls (and a normal map created from a grayscale/bumpmap version of the texture). However, I've also tried changing between all non-round Unity Standard Models with no result.
3. The lines are indeed dependent on Camera Distance (both Editor and ingame Camera). If I move the walls, the lines stay at the same position on the walls (like on a certain spherical radius around the camera). If I move the camera (editor and ingame camera display different lines) the lines move together with it.

Do you have any idea what's going on/what I can do to prevent those lines from appearing?

Thank you in advance! :)

Answer 1

So it seems that the problem was actually the auto-generated MipMap on the normal Map. At certain distances from the camera the decreased MipMap quality lead to the mentioned rendering artifacts/problems. Turning off the MipMaps (Located within the Import Settings of the Texture under Advanced -> Generate Mip Map) solved the problem. Alternative solution: Set the Filter Mode of the Texture to Trilinear (instead of turning off the MipMap)