Please Help: Texture defects, no idea where they come from

Hi, im working on a scene for an industrial production and suddenly this problem occurs on my textures. I am using a PBR roughness / metallic workflow.

100% Black Base texture RGB. Tried also png/tga format with 8bit, 8bit dithered and 16bit and 16bit dithered. Just to be thorough.

I get these flaky artifacts on the albedo. No idea where it comes from. (the green and purble spots)
Does anyone has an idea?