Uh-oh. You’re in hot water now.

Francis Ford Coppola will soon premiere at the Cannes Film Festival a film on which he has risked everything that’s arriving clouded by rumors of production turmoil. Sound familiar? On Thursday Coppola’s self-financed opus “Megalopolis” will make its much-awaited premiere. Other films are debuting in Cannes with more fanfare and hype, but none has quite the curiosity of “Megalopolis,” the first film by the 85-year-old filmmaker in 13 years. Coppola put $120 million of his own money into it. Forty-five years ago, something very similar played out when Coppola was toiling over the edit for “Apocalypse Now.”

It would be a challenging undertaking for any filmmaker to attempt to represent the outsize talent, unique style and utterly devastating downf…