Low spot on the mesh

I have a v core 3.1 enclosed and I've already applied the magnetic pad and metal sheet. I've found only after doing it that it wasn't supposed to be made in this order. However I still managed to get a decent bed mesh after some trial and errors. I ended up with this mesh, and here's my problem. The blue low spot doesn't move no mater the adjustments I did on the frame. How can I fix this ?