Hi,
I honestly can’t see much from that video, probably due to heavy compression. If you mean the shadow popping in the grass, that is most likely not related to the Scatter plugin in any way, but a matter of LODs. Some assets tend to either have dynamic shadows disabled for LOD levels higher than 0, or even swap to completely shadow-less 2D card. So if that is the issue you mean, then I’d suggest you explore the given asset in static mesh editor and see how LODs are set up there.