I watched the film, and there’s a brief shot where Lennon surreptitiously takes some small item out of his pocket, notices that the camera is on him and then puts it back in his pocket. Not sure what was going on there, but my hunch was some sort of drug use. There are definitely days in the documentary where Lennon seems strung out on something. Helluva musician, though.
Well Lennon did make a song called "Cold Turkey" made a few months later.
His constant breaking into “Don’t Let Me Down” got really annoying!