Most movie directors do a great job of bringing their vision of the script to life on the big screen, their control over each shot in the film quite obvious, but a good director also knows when to leave in the happy accidents.
Which is why a surprisingly high number of popular films still contain happy accidents, because Titanic wouldn't have been the same without Leonardo DiCaprio getting tongue tied when he asked Kate Winslet to pose for a sketch.
And remember when Star-Lord dropped the ball in Guardians Of The Galaxy?
That was Pratt literally fumbling the ball in a blooper too fun to cut, but at least he didn't break that prop, unlike Kurt Russell in The Hateful Eight- who smashed a $40,000 antique guitar by mistake:
Quentin Tarantino was loaned a 19th century guitar for Jennifer Jason Leigh's outlaw Daisy Domergue to play in The Hateful Eight. A prop was provided for Kurt Russell to destroy...only for him to smash up the real, $40,000 one by mistake.
Leigh's horror on screen is genuine, and Russell was suitably mortified about obliterating an irreplaceable antique.