A Final Cut for Orson: 40 Years in the Making (2018)
https://www.youtube.com/watch?v=kl3jKWm7yJo - from the Jason Brahms YouTube channel (39 mins.)

The blurb (from IMDb):
“A glimpse behind the scenes into the complicated process of recovering and completing the final film of legendary director Orson Welles.”

Also worth checking out is the feature-length documentary “They’ll Love Me When I’m Dead”, streaming on Netflix.
I find the film “The Other Side of the Wind” both brilliant and frustrating. It’s something about the slapdash nature of some scenes and some awkward and unnatural sounding dialog. The film was apparently largely improvised and it definitely shows, not the fault of the people who finally had to put the film together. The 35mm film-within-a-film scenes were excellent though. It’s a bit like Alien 3 for me: I enjoyed watching the making of the film more than the film itself.