They are all either quads or tris. I have checked all of the quads. It WAS 3am, but I'm pretty sure I deleted the suspicious faces and recreated them with Append To Polygon.

The ear was difficult without tris, especially the folds and creases inside it.

If you think that that's what's causing it, Mike, then I'll revisit my n-gon hunting spree.

Thanks a mill.