I just downloaded 2.31 and installed. To just get an idea of what it does compared to 2.30 I did a quick render and was rather shocked. Look at the results... exact same .blend file all I did was hit render in 2.30 and 2.31.
This is the 2.30 image
And this is the same in 2.31
I used a lambert/toon combo, no textures, 3 lamps, pretty basic. Anyone have a clue what this may be???
Here's two more images with discrepancies:
Find the differences! Very obviously the wheel at the right bottom. also the "gears" there. and there's more if you look closely.
This might have something to do with Auto Smooth. Because of a bug Auto Smooth was always on in Blender 2.28c and 2.30.
Try enabling Auto Smooth on your objects and see if it helps.
had another look and experimented a bit... the big difference seems to only occur when you use set smooth in blender 2.31
Ghost that's it!
When I set smooth without auto smooth on I get the flawed result. With autosmooth it's as before.