When this happens to me I break the pattern. I mean instead of turning my time into beta testing for SM, I move or delete the lights. Change them..delete the ibl and put a similar hdr on the sphere instead. Lower or raise light bias . Use shadowcams to be sure light is actually hitting the target.. Adding a specular only light as your secondary light. This light can have diffuse gray if you want light from it too.  Make parts or clothing invisible to RayTrace

Switch off light emitter on cloth and hair. Save your successful lightsets as PZ3s and start fresh from there. All this in 10 minutes so you can have fun again..

Until that IDL fix is released  ;)