Continuity mistake: In the scene where Shooter is with the other pro golfers, (the ones with the gold jackets) and they're drinking wine, Happy interrupts them wearing an ACDC top. Notice Shooter's wine glass switch hands a number of times, and when he tells Happy to meet them on the 9th green, the wine glass has disappeared totally.
Other mistake: When Bob Barker reaches up to grab Happy by the neck, his head is resting on the grass immediately before and after that shot. Happy was standing fully upright, so there's no way Bob Barker's arm could have been that long.
Continuity mistake: On the last hole, Shooter McGavin overshoots the hole and the ball ends up going past the green. However once he shoots the ball off the man's foot and onto the green, we now see him coming onto the green from the fairway side at the bottom of the screen, not from behind the green past the hole.
Plot hole: The bet between Happy and Shooter is prohibited, probably legally, but also definitely according to PGA regulations. It is prohibited for any professional athlete to gamble, on their sport in general and certainly on their own performance. Both of them could get suspended or banned from Pro Golf for this, and Shooter would certainly know it.