Previewing in Eevee looks fine, but when I switch to Cycles, this occurs:
As you can see, parts become darker; there's black, ink-like stuff on the model (I thought it was AO at first and disabled it, but it's still there); and the faces of the model can be seen, especially along the chest and R-Leg.
The material setup is just the default BSDF with a Base Color (.jpg) and Normal map (.png) (fed through Mormal Map node).
Neither have been exported as an image, just rendered in the viewport.
Any advice appreciated - first day on Blender (well, near enough)