Strange Mesh Decal Artifacts

Hello everyone,

I am using a mesh decal for the first time and I am getting these artifacts.

Can anyone tell me how to get rid of these? Maybe with depth information?

Strange is that this artifact doesn´t appear in front of the sky as you can see in one of the screenshots. To be exact, it´s still there as you can see in the pink colored mesh decal example, but pretty transparent.

Note that the normal map I used in the decal material is mapped wrong and to strong in one area, so one dark line looks like a artifact, but is just shadows and not what I mean.

Thanks for any help.