When young Jim Hawkins enters the Cask and Anchor Tavern to apologize to Long John Silver, the top four buttons of Hawkins' leather vest are properly buttoned. The close-up shots of their conversation reveal only three of the four buttons are through the button holes.
With a number of pirates in prison one of their free mates with a horse and cart stops outside the jail and ties one end of a rope to the cell bars and throws the other end into the cart without tying it to anything. Despite this he pulls the window and half the wall down.
When Israel Hands falls to his death on the rocks, it is obviously a dummy that is seen heading over the edge.
Long John says a long time has passed since Treasure Island, yet Jim is the same age.