Opie never takes the first gumball from David's hand. When David drops a second gumball into Opie's hand, it's into an empty hand, and Opie, without reaching for anything, has a big wad in his cheek.
The Acorn and Oak gumball machines shown here cannot dispense a gumball without the handle turning. The gumball machines use a rotating plate to capture and then dispense the gum. Although Mr Browne is shown using a wire to "jimmy" the machine, this is not possible as the machines are sealed and there is nothing to jimmy that would facilitate moving the gumball into the dispensing location.
When Andy and Dave are talking in the sheriff's office near the end of the show, a train whistle is heard in the distance. In the U.S., by 1960 steam locomotives had been replaced by diesel engines, which had horns instead of whistles. So the sound they heard should have been a horn, not a whistle.
When Andy puts the key in the lock of the cell door to let David Browne out of jail, he opens the door without turning the key.