Reply To: this edge on the left is not behaving well as the other one
The third pcture is in Front View. From Bottom View, it is this side and zoomed in, you can see the error:
To remedy that Shading problem you get, you could try adjusting the Weight of that Edge, or the Angle of the Smooth By Angle Modifier, or jus Select this Face and set it to Shade Flat (CTRL+F > Shade Flat):
