NOTE: please, enlarge every image to notice the issues.
Dirty ‘whity-sketchy’ artifacts (like tons of little lines) around actors’ edges or borders. More noticeables (but not only) when using lights’ source radius higher than 0:
The right object is lit, even being in a shadowed area. It seems like an incompatibility between the Megascans master material and the ray traced shadows, so some nodes must be destroying the shadowing:
‘Halo’ artifacts around the sphere and around the letters of the floatting text over the Floor mesh, due to ray traced reflections (and/or RT shadows, maybe) and the difference between actors’ roughnesses, as far as I noticed.
Extrange kind of ‘Global Illumination’ shadowing around the sphere, projected on the floor, even if GI is totally disabled, so they may be some kind of stains or compression artifacts, but no GI.
You can check the original scenes too: Dropbox - BUG-RT_artifacts.zip - Simplify your life
Thank you.