I don't know what's going on.. i tried to line up all the vertices (S, Z, 0) time and time again with no difference whatsover.
Same goes for the back of the model
Link to blender file: https://we.tl/t-cPg3KxVGnO
I fixed it! i don't know if it's a good solution long term but i just applied mark sharp on the edges that were causing problems