Great workprint, I absolutely admire the work you guys put into restoring Star Wars and I think it clearly shows how great of a cleanup you did on the movie. Can't wait to see the final result:-)

However, I agree with Harmy on the matter of compression artifacts. There's so much blocking not only in dark scenes like the one in the canyon, but rather throughout the whole workprint, so much that it "eats up" a lot of the grain structure that would otherwise probably be visible.

By looking at the encoding settings (MediaInfo can do that) it is obvious that encoding speed has been a major goal, which comes as no surprise considering this is just a workprint. However, the settings could have been significantly optimised to achieve a better quality with less blocking and yet without a drastic slowdown. F.e. encoding with 1-pass constant bitrate as you did is much inferior to CRF mode quality-wise.