When Silver and his supporters row in the jolly boat to the island there are 9 men in the boat. Then, when they storm the stockade, four are killed in the ensuing fight before Silver and the survivors retreat to the beach. Yet there are still eight men alive.
After Jim has killed Israel Hands he leaves the Hispaniola on the beach with the mainsail unfurled and returns to the stockade. When he and the others return to the ship, the sail is furled.
At the end of the film, Jim Hawkins' mother is looking out to the arriving ship. There is snow falling. The camera cuts to Jim Hawkins on the ship, looking towards the land. The sun is shining and he just has a simple shirt on.
During the keel hauling, the victim is hauled feet first under the ship and comes back up the other side head first.
As the Hispaniola leaves Bristol port you can clearly see a stud linked anchor chain, this was not invented until 1819.
When Ben Gunn is talking to Jim Hawkins at the blockade on the island, just before the fight, you can clearly see a fine mesh, which seems to be peeling off, on Ben Gunn's chin which is holding his beard and moustache on.
As the ship gets underway the first time, the order is given to "hoist the main sail". Fore-and-aft sails are hoisted, but the ship's main sail is square-rigged. Square sails on ships of that time were unfurled, not hoisted.
There is an aerial shot of the Hispaniola in the open sea on her outbound voyage with no sails set at all yet there is clearly a wake behind the ship suggesting that she has an engine.
Silver was supposed to have his left leg missing.