That most likely can be fixed by changing your irradiance map settings. There's an option to "Check sample visibility" that you can enable. You can also increase your "Max rate" to -1 or 0. Lastly, you can increase your HSph. Subdivs to 70 or 90 - which helps with splotchy shadow areas. Worst comes to worst, you can enable Detail Enhancement, but that means longer render times.
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