The example I posted was using 30 spatial and 3 temporal. After your comment, I bumped it higher and could watch the render get iteratively better as subsamples were added in the render preview. It took to around 1800 subsamples until it looked like the screenshot with Megalights disabled (the correct ground shadow). It didn’t seem to matter if it was high temporal or high spatial as long as the combined hit 1800 subsamples, the shadow was fixed (so 42 by 42 worked, also 180 by 10 etc)
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