I am having this texture shading issue with this model and it appears to be from the normal map node. After disconnecting and connecting the normal map node into the Principled, with and without the bump node, it appears that it is coming from those (the normal map node specifically).
I tried recalculating the normals, flipping the normals (used backface culling to check), and tried it out with different color textures and normal map textures, and I still get the same shading issues in the exact same place. This normal map isn't baked, the model is using tris, and is barely sculpted out. The lighting has nothing to do with this as well.
I had previously asked on Reddit and one person and I were going back and forth constantly trying to solve this issue. The closest thing we could get to was that it could have been a problem with the mesh itself. He said something that normal maps on curved geometry could cause issues.
Here is what the problem looks like in the rendered viewport (results are the same in the final render) and my simple node set up:
Anybody have any ideas on what the problem could be?
Here's a demo blend file download if anything: Thanks to anyone for helping! https://www.mediafire.com/file/s76aac1znbil0fq/MeguminStaff_%2528demo_file%2529.blend.zip/file