Rendering via DR? If so, is FP the same version everywhere?
Nope, no Distributed Rendering here.
I know that it looks like a bucket inconsistency problem but, believe it or not, this preview was made with progressive image sampler.
What's interesting during the light cache prepass the shadows look normal.
Another weird observation:
With global material override turned on (default gray VrMtl) everything renders fine. The same override with "Preserve original: reflections, refractions" turned on - the problem is back.
Another thing worth noting is that within the scattered group there are some instances of CAD Vizblock objects, but I don't know if it's relevant.