Flat surface not being shaded consistently across quads I've been working on a mesh and realised that part of it is not being shaded consistently across the borders of each quad. I've isolated the section into its own blend file and cannot figure out what's causing the issue.

The section in question is a flat plane with some loop cuts. It's set to flat shading and the face normals are all consistent and pointing in the same direction. There is no modifiers applied.



Does anyone know the cause of this and how to correct it?

Blend file can be downloaded here: https://drive.google.com/file/d/1DW8WcC2wAT3FR1h9uUGkHZmDef-mzgR3/view?usp=sharing
While deactivating the "Auto Smooth" helps at the moment, i believe that something else happened and messed the normals up. 

In my humble opinion i think that the surface should be fine even if the Normals are set to "Auto Smooth", in that regard i checked and found that if you press Alt+N and use the "Set From Faces" option, the surface normals are corrected.

Here the visual confirmation: