Paint-layer on top of Stack blens through layers below

Hi Community,
Got into an "issue" by adding a Texture via a Paintlayer.
Setup of Paintlayer is: DIFFUSE-TEXTURE and NORMAL-TEXTURE.
I'm trying to add a texture on the very top of the Stack, but  it blends through all the layers below.
Paint-Layer's blend mode is NORMAL.
Still don't get the sense why the layers below affect a layer above.
Is there something I didn't take into account ?
Olli