I am using the map normal as a stencil. The map has transparency. The layer blend function is set to normal.
The problem is that Substance Painter ignores the transparency of the normal map. It paints an element, but it also removes normal information from the layer below where the stencil should be transparent.
This problem does not exist with map alebedo, or hight. These maps accept transparency.
Using a stencil that has transparency and normal maps, is impossible. If the object is complex, like an ornament. The normal information from the layer below is removed where it should be, i.e. where the stencil is transparent.
It looks like a bug, especially that other maps (color, hight) accentuate transparency.
I had this same issue with Metallic stencils, until I tried to import as Alpha, then the issue was resolved. Assets that are imported as "texture" and "alpha" behave differently, regardless of the alpha channel the texture has (alpha shows in Assets and Viewport for Texture assets)