I recommend all of these documentaries
The Ghost of Peter Sellers is about the making of Ghost in the Noonday Sun (1974). Sellers basically undermined the production. The most amazing incident: He had a heart attack and was hospitalized in Cyprus where the film was shooting. Two days later he was socializing in England as shown in a newspaper.
This is one of two films in this group that was damaged by Marlon Brando’s erratic behavior
This one is about a low-budget Fantastic Four film that was completed but never released.
Hearts of Darkness is an outstanding film about Eleanor Coppola’s documentation of the troubled filming of Apocalypse Now (which included Brando).