Continuity mistake: Blackbeard kicks Barbossa's wooden leg and makes him fall next to a rock. A frame later Barbossa is about two meters away from it. (01:52:55)
Continuity mistake: After Gibbs burns the map in front of Barbossa it cuts to Jack waking up, and when he falls onto the floor this closeup is a flipped shot. Note the ring on Jack's right thumb which should be on his left, and all his hair trinkets are backwards.
Continuity mistake: When Blackbeard falls semi-dead, his left arm lays by his side, yet a mere frame later it's extended.
Continuity mistake: When the movie ends, Barbossa is given his hat with no feather. A frame later the feather appears. (02:04:55)
Continuity mistake: Near the end of the movie, when Jack is talking to Angelica on the deserted island before leaving her, you can see the gold earring in her left ear in the shot over her shoulder facing Jack. In the next shot, over Jack's shoulder, her hair is covering her left ear. Then another shot from behind Angelica, and you can see her earring again. And a final shot from behind Jack, where Angelica's ear is covered again.
Continuity mistake: When Philip asks the mermaid to give him back his life, the position of her hands keeps changing between shots.
Continuity mistake: While handcuffed to a chair, Jack tries to grab a cream puff. The napkin on the left alternates between being closer and further away from the dish between shots, and also swaps between being wrinkled to flat.
Continuity mistake: When Angelica is about to take a leap into the cliff, Philip tries to stop her. When the angle changes, he is standing still and running towards her again.
Continuity mistake: After Philip blocks the tank's lid with a bible, the mermaid's head position keeps changing in every single shot.
Continuity mistake: During the trial, Jack's hand swaps back and forth between raised in the front shots, to lowered in the back shots.
Continuity mistake: When the mermaid approaches the pirates' boat after being threatened with a knife, her arm is uncovered in the shot from behind, but covered in hair in the front shot.
Continuity mistake: When the castaway is brought to the Spanish king, he raises his hand, but in the very next shot it's lowered.
Continuity mistake: By the big tree, when Philip is talking with the mermaid, a bang of hair by her right temple appears/disappears between shots.
Continuity mistake: Jack is on top of a carriage which makes a right turn and encounters a second carriage, which drives parallel to it. For a brief second, there's an aerial shot of Jack with the guards chasing him and the second carriage disappears, only to reappear a frame later.
Continuity mistake: While in the cave with Jack, Angélica's grip on the knife differs between the front and back shots, with the handle more visible in the back shots.
Other mistake: In the cave, Angélica steps out of the water and in the close-up of her face her hair is dry, and even drier in the following close-up.
Continuity mistake: In the cave, Angélica steps out of the water, knife in her hand, and her fringe changes style all the time, most noticeably when she asks "Why?".
Continuity mistake: Philip insists the mermaid on getting his life back, strokes the hair around her ear, but a frame later his hand is by her temple.
Continuity mistake: While fighting against Blackbeard in the fountain of youth, Barbossa falls down and bends completely forward to help himself up. When the angle changes he is in a different position, about to stand up.
Continuity mistake: When Angelica is about to tell Jack that she loves him, his position alternates back and forth between being perpendicular to her a meter away, to face to face at half a meter distance.
Chosen answer: She most likely went to stop the ritual, she probably didn't want her tear to be used by the likes of Blackbeard. She knew that Jack would use it wisely.