Texture paint changes size and doubles in Layout mode

Question

I Texture a house and want to put some "Wet spots" on it. I am using 2 Shaders with a Image Textures as mask. So I have the 2 Shaders go into a mix Shader with a Image texture that goes into the FAC of the mix shader. As Image Texture I create a Textures Paint in which I use leakage textures to paint the spots.

I first did the window frames wich worked nice.

Then I did th wall but when I exist texture paint it suddenly looks way different.

Inside Texture Paint:

Inside Layout Mode:

I already tried a bit of stuff because I just thaught my settings are wrong or I mixed up a textures but I cant find the error that is causing this.

I used a Concrete texture for the wall which i copied and mixed with a brick textures. The same texture I copied on my windows. My textures look like this:

Window:

Wall:

Answer 1

Unless you use a Texture Coordinate node to specify the Vector input of the Image Texture node then it goes with the default, usually Generated, “automatically-generated texture coordinates from the vertex positions . . . over the bounding box of the undeformed mesh”. That can change like you've shown for several reasons, one of them being applying object transforms.

For the method you're using to work consistently your mesh should have good UV mapping, and your Image Texture node's Vector input should be using the UV output of a Texture Coordinate node:

In the example above I've painted a tear-track on an image texture which I'm using as the Factor mask of an RGB Mix node -- because Suzanne is UV mapped, and I've used the UV output of the Texture Coordinate node in the Vector input of the Image Texture node, the tear-track is correctly positioned under Suzanne's eye.