Even in a boxing film where the fight and "Script" has been written for ages still goes wrong.
In Rocky 1, I think in approx. Round 7 or 8, at the end of the round Carl Weathers and Sylvester Stallone get properly unhappy with each other, they weren't acting at this point as they both landed big just before the bell, totally outside the script.
They kept it in the film but it's impossible to do.
Someone can move forward into a shot accidently, if they get knocked out the script, even if they are supposed to win means absolutely nothing.