Shadows behaving oddly with material and doesn't match solid view

I’ve been trying out ‘painterly’ materials for my model as someone very new to blender, but for some reason, the shadows in the solid viewport vs the material render don’t match at all. The BSDF on its own has normal shadows but as soon as I add the voronoi texture and texture coordinate into the material, it becomes weird again.

I don’t believe the normals are off. I’ve reset them with shift-N and they’re all the right direction. I’ve tried remaking the shader (since I recently upgraded my version of blender from 3.something to 4.something), subdividing, changing topology, etc but the shadows won’t appear as they do in the solid viewport. I want the upper lip in shadow like it is in the solid viewport. Any ideas on how to fix this?

The solid viewport doesn’t use shaders; the material render is using it. They don’t match because it’s 2 completely different view modes.

(And small FYI: None of this involves shadows. Diffuse Unlit Area ≠ Shadow.)

EDIT: I didn’t see your edit until after I sent this, mb. Would you be able to elaborate any on what you mean by a diffuse unlit area? I don’t think I’ve learned much about that yet.

I’m aware of that, though I’m thankful for your input. I more so mean that it did look normal at some point and I don’t know why it doesn’t now. This is how a similar material looked on the previous version of this model. I’m trying to get back to this. The two nodes used in this material don’t seem like they should have this effect as they didn’t in the videos I learned them from.

That was mentioned just to clarify that sometimes knowing/using the right terminology can help.

It’s basically the difference of:

  1. This part of the mesh is darker, because there is not a light hitting that area, and making it brighter.
    vs
  2. This part of the mesh is darker, because something is casting a shadow on it.

Think of it like real life.