Texture paint brushes paint in random places of the model when trying to remove texture seams

I have a model that has textures which I want to connect through the soften brush in texture paint mode. The problem is that, when I paint the model through the viewport, the texture gets painted somewhere else. Is there a way to solve this?

I’ve heard that this may be due to bad UV unwrap, but I unwrapped in every way possible, and I just can’t get it to work. For now, I have stayed with smart UV project, and I made the texture according to this unwrap.

Also, is there a better way to remove seams in textures? I’m using texture paint because I find it to be very effective, but it doesn’t work now. So, if anyone knows another way to remove these seams I would really appreciate it.

(Btw, with seams, I refer to these cuts):

Check for reversed normals, duplicated faces or not connected vertices in your model. Maybe it is not problem with UV but with geometry.

Thank you so much, I just had to recalculate all the normals in the mesh