I have this fairly basic scene with all meshes using (materials with) Toon shading. I have the render mostly as I want it, but there are a few problems with it. If you look at the D-pad (the model in the scene is a gamepad) closely, you can see some uneven shading, a bit like crumpled paper; the diagonal, ovoid buttons have black lines partway along one side; and the circular buttons are not filled in with the colour of their materials, and have some grey from surrounding object.
I have very little experience with 3D modelling, so while I understand the basic concepts involved here, I have no idea what is causing these rendering quirks. Can anyone offer any advice?