Strange artifacts with enlighten without overlapping or wrong lighting UVS and high quality lighting settings. It feels like enlighten is doing wrong.

I've done scene lighting and render lighting allot of times in Unity and also in unreal. And yes i know the differences between dynamic and baked lighting and also use this lighting settings and lightmass. I know about the generate UV section for lightmaps and i also know how to make lightmap UV's by myself. I am working with quite complex models at the moment and i'll keep getting some strange behaviours when building my light. I stumbled on a problem i can't answer myself.

The first thing is that every light build is quite inconsistent. What i mean is that at one time when i am building some in my opinion difficult places the lightmaps are artifact free and really clean. But sometimes when i add more models like a car chair or re-position them and build again. Then unity gives me some strange ugly stripes with extreme contrast differences on these difficult places. If i am adding then again more models or re-position them and build once again!, then it will remove these artifacts on some places but it ads them on other places.

This is how it looks: some bakes are clean and looks really nice. I got also my chairs placed on the right position. But then when i remove my chairs or replace them those stripes are appearing.

As you see i am getting this strange ugly black contrast stripes without changing my uvs and without changing my lightsettings. i only removed or replaced my chairs and those chairs are a completely different object. I only use 1 directional light that is fully baked and one baked reflection probe. The problem is also not a compression or a mipmap problem.

Does somebody knows what this problem is and how to solve it or explain it. Thanks sincerely Arno