The following contains SPOILERS for Pirates of the Caribbean: Dead Men Tell No Tales. If you haven't seen the movie yet, bookmark this, and return once you have.
One of the more entertaining aspects of Pirates of the Caribbean: Dead Men Tell No Tales, is the way it expands on the history of Captain Jack Sparrow. We get to see the moment that young Jackie actually becomes Jack Sparrow. We learn how he first became a captain, and where he got his hat. We also learn how he obtained his special compass, which has become a vital part of the franchise's history. The only problem, we already knew how he got the compass, and this wasn't it.
Jack Sparrow's compass receives one of the great introductions in movie history. It's dismissed at the beginning of the first film as a "compass that doesn't point north," an indication that Jack Sparrow is something of a joke as a sailor. However, later we learn that the reason the compass doesn't point north, is that the holder isn't looking for north. The compass is magical, and it points toward that which the holder most desires, be that treasure, love, or really anything at all. It leads Jack to the Isle de la Muerta in the first film, to the heart of Davy Jones in the second, and helps Gibbs get back the Black Pearl in On Stranger Tides. Whatever happens in these movies, the compass is the thing that helps drive the characters toward the action.
While we have never learned exactly where the compass came from, Pirates of the Caribbean: Dead Men Tell No Tales, shows us how Jack came by it. It was previously owned by the captain of the Wicked Wench, a ship on which Jack was the first mate. In the pirates' coordinated attack on Salazar, the captain of the Wench is killed and as he dies, he passes command of the ship, and the compass, to Jack. Jack then uses the compass to defeat Salazar, and our story continues from there.
Except we already knew where Jack got the compass, and it wasn't the hands of a dying captain. In Pirates of the Caribbean: Dead Man's Chest, Jack's crew meets up with Tia Dalma, a witch, who they believe can help them find the key that Jack knows he can use to get the upper hand on Davy Jones. At first, the witch is confused, because she's already given Jack something which should be able to help him find it. She asks him about the compass which Jack Sparrow bartered from her, and why it can't help him. Check out the video below at about the 2:10 mark.
The line is brief and ultimately unimportant to the plot of the original trilogy, and so it's never brought up again, but there it is. Jack Sparrow got the compass from Tia Dalma, who is actually the sea goddess Calypso, not the captain of the Wicked Wench. Pirates of the Caribbean: Dead Men Tell No Tales appears to have completely retconned the history of the compass.
We know that Jack Sparrow could not have given up the compass after the events in the flashback, as doing so would have brought about the freedom of Salazar, as it does in the new film. It's possible, perhaps, that Jack had the compass stolen from him at some point, we've seen that happen, and he then had to barter with Tia Dalma in order to get it back, but does that make sense? Why would Jack Sparrow, of all people, be willing to barter for something that he believed was his? Even if Tia Dalma wasn't the one who actually stole it, why would a pirate be willing to make a deal for something when just taking it makes so much more sense? He's a pirate, he doesn't barter for things that don't belong to him.
The change in the history certainly makes more sense as far as the plot of the new movie goes. The compass is vital to the story and bringing Tia Dalma into it would have likely required a seriously large shoehorn. Still, the fact that the previous backstory wasn't even dealt with is odd. Terry Rossio has been a credited writer for the entire Pirates of the Caribbean franchise, including the newest film, and one would think he would have noticed the continuity issue being presented. A couple lines of dialogue might have been all that was needed to say, here's why that other bit isn't really true.
Perhaps, if we get another Pirates movie, this discrepancy can be explained. If not, it's probably no big deal. Nobody rewatches the sequels in this franchise anyway.