Texture painting and seams

So I was texture painting my character’s face and run into a problem.
My character is too big and complex to upload I think, so here is some simple example.
I have one cube with a seam cutting it in the middle and two UV textures: one is for the simple unwrap and one is for the project from view unwrap. So I’m trying to copy projected picture into the first unwrapped texture.
The problem is I can see my seam in the middle after doing this.
Here is a screencap:
Right in the middle.
Here is the .blend file, you can start texture painting and see it by yourself:
Is there a way to fix that issue?