if others didn't mention, some errors in  shader tree, e.g. diffuse + specular > 1, refl lite mult is checked.  some problems in render settings, e.g. HSV 2.2 is used instead of gamma 2.2.  this render may also not warrant shade rate 0.1 and pix samples 18.  maybe 0.5 and 6 would be adequate at this point.  somebody double-check if shading rate of 0.2 in object properties over-rides shading rate of 0.1 in render settings, or vice versa.