Revealing mistake: When Dracula goes to grab the cell bars on the window to free Reinfeld, the bars are obviously not metal as they shake and have a slight bend to them.
Continuity mistake: When Dracula calls to Renfield for help in the ship's cargo hold, Renfield opens the doors and the right side of his hair is completely wet. But when Renfield runs down to the coffin and grabs it, his hair is totally dry.
Continuity mistake: In the scene where Renfield is locked up in the sanitarium cell, the camera first zooms in to the horizontal bars on his window. Some shots later, the camera shows the guard looking under the doorflap, and since the door is opposite the window, the shadow of the bars fall on it. The bars have suddenly changed to a criss-cross pattern.
Continuity mistake: After Dracula abducts Mina, they dance in Carfax. Mina is wearing shoes with 2" heels, but she was barefoot when she got out of bed.
Continuity mistake: After Dracula introduces himself to Renfield, he goes up the stairs. For a moment you can see his shadow on Renfield, yet after they go up the stairs, the shadow gets up whining.
Revealing mistake: As Mina is dancing with Dracula in the ball, we can see that in the mirror, she seems to be floating. Later on, as she is held by the arm and leg and spun around, we can see in the mirror that everything is in slow motion, even the orchestra conductor and a guest holding a fan.
Continuity mistake: At the end of Dracula's dance with Mina in the ball, as he is about to shatter the mirror which has given himself away, he throws a table at it. Mina is shocked, but as the camera shot changes to one of the mirror and the table approaching it, we can see that Mina is looking perfectly calm.
Continuity mistake: When Renfield enters Lucy's room he pulls off all the garlic on the far bar above her bed. He looks under the sheet, and as Lucy wakes up screaming and he stands up, the garlic on the far bar has reappeared.
Other mistake: When they are trying to figure out who the vampire is and they hold a ball and then they pull down a curtain and reveal a mirror it is obvious in the reflection that Mina has no partner and when they do their "finale" when Dracula is lifting her up it is obvious Mina has some other support that will continue to turn her after she is shown in the mirror while the vampire has no reflection.
Visible crew/equipment: When Dracula is climbing down to Renfield's window, a wire is visible moving against the side of the building above Dracula.
Answer: A clip from Mutiny on the Bounty is used in the ship scene. I believe it's on deck before Renfield and Dracula are seen. The premature burial is the scene when Lucy's coffin is being carried on the moors.