During his conversation with the doctor, just before they go to see Squire Trelawney with the map, a long piece of hay (at around 22 mins) disappears (at around 28 mins) then reappears (at around 38 mins) from Jim Hawkin's left shoulder.
When Silver tells Jim that the island is a dot on the horizon, the faint outline of a broad land mass in the fog stretches across the screen (at around 56 mins).
At 56:22 the Squire calls out to one of his men, "Are you all right Reverend?" But the Squire's gamekeeper is Redruth. At 01:17:37 the Squire clearly says "Thank you, Redruth" to the same heavyset bearded man.