Blocky artifacts are the result of poor bitrates. In streaming services it’s due to over compressing the stream, which is why you see it when part of a scene is still or during dark scenes. It’s due to the service cheaping out and sending UHD video at 720p bitrates.

I’ve done that click and drag many times. Nothing worse than accidentally dragging a folder designated with pseudo random numbers into another pseudo random numbered folder, and not knowing if you actually dragged it into a folder, or missed and did nothing

This seems to only be true in conservative States.