First try rendering without ray traced shadows. If the artifacts clear up without shadows you'll know this is the culprit..Typically polygonal shadowing artifacts such as I see in your example are caused by a too low min bias rate on your shadow light. Looking at your setting of 0.800 contradicts this as it's a relatively high setting, usually those kind of artifacts begin showing up at settings of less than 0.200. Still, experimenting with Pixel Samples or Min bias rate might reveal something. You might try test rendering with a min bias rate of around 0.350 and see if the artifacts get worse or better. As far as AO... have you tried disabling AO on your scene/materials to determine if that's actually the cause?

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