When I was a young child, circa 1975, I saw part of a movie on TV in the UK. It was a black and white set.
It was set on a sailing ship, probably 18th or 17th century. A scene I remember showed the ship arriving at the charted location of an island but it wasn't there. A character, probably the captain, said "[Island name] is somewhere else" then with a quill pen drew a line through the island on the map.
It may have been an older movie. From what I remember it looked similar to the Captain Hornblower movie from 1951. I'd guess it was a similar date.
The cast, at least the Captain was probably British.
It wasn't Mutiny On The Bounty, neither 1935, or 1962, or 1984. The discovery of Pitcairn where it wasn't supposed to be is pretty much the opposite of my memory.
Additional information. Note that this is 50-year old memory of something my parents were watching when I was very young. I probably only saw the one scene.
I saw it probably on BBC1.
It was likely aimed at grown ups.
It was a period piece with production values similar to Captain Horatio Hornblower 1951. Not sure if that would be high budget for the time.
No idea what the captain's name was, or if there was any love interest.
The captain seemed neither particularly happy or sad. Perhaps moderately amused that the charts were wrong, but it didn't seem like any kind of big deal either way.
I presume the captain was talking to one of his officers.