Just before dancing with Dracula, Lucy flips over the record on the player and sets it playing again. The record is moving around at a leisurely pace; however, the earliest disc recordings played at around 78 RPM - a much faster speed. Records playable at lower rates were much later inventions.
Lucy awakens to Mina's shallow breathing and rings for Seward, who comes to the aid, followed by Jonathan. As Mina dies, and Seward closes her eyes - you can still see her chest rise slightly even though she's supposed to be dead. In the following far shot, as Jonathan is steering a grieved Lucy out of the room, you can still see Mina's chest slightly rise again.
The film calls Dracula's victim (Lucy Westenra in the novel) "Mina," makes her Abraham van Helsing's daughter, and goes to some lengths to establish her Dutch credentials, even having her speak the language at one point. While some might question the pronunciation of Mina's name, but as it is short for Wilhelmina, the pronunciation is correct.
After the vampire woman jumps through the window, Annie chases her down the corridor. Approaching the window (from her POV) we can see that the central part of the broken frame is dangling, and swinging from side to side. The view switches to outside the window (looking into the building), and the broken frame is suddenly no longer swinging.
When Harker is driving away from Dracula's castle after having Dracula sign the deed papers, Renfield jumps him from the back of his car. During the scenes of struggle, there's a from-the-front shot that clearly shows another car loaded with people (crew?) about a hundred feet or so behind the Harker car.
When Dracula appears outside Mina's window he attempts to open it by turning the latch and the latch inside starts to to turn, however there would be no latch on the outside of the window thus he had to remove a pane of glass and reach through.
When undead Mina approaches Van Helsing in the mines under the graveyard, her reflection is seen in the water. When, two scenes later, Count Dracula comes into Mina's home and walks by a mirror, Van Helsing points out that he did not see Dracula in the mirror. That Lucy does cast a reflection in the water, where she ordinarily should not have, is explainable by the fact that, just before her reflection became visible, Van Helsing had dropped a crucifix into the water. That had the effect of sanctifying the water--of making it holy water, in other words; though they cast no reflections in glass or polished metals, vampires (according to one obscure detail of the superstitions about them) WILL reflect in holy water, which is the only substance capable of showing vestigial remnants of the souls they lost to damnation when they died as living beings.
When Dracula transforms into a bat and attacks Renfield in Carfax, he falls backwards, rolls over a crate and down the stairs, colliding with the "stone" balustrade as he falls (and causing it to wobble).
A common problem with many vampire movies is repeated here: the bite marks on the ladies' necks are placed in such a way that the vampire's teeth would have to be one behind the other, not along side each other. The placement of the bites would have Dracula performing a serious contortionist act to get his teeth into the willing victims.
VanHelsing (surrounded by the men) prepares to "purify" his now 'undead' Mina As Seward and Harker question her actual state, VanHelsing holds up a small mirror for them, insisting Mina casts no reflection. As Jonathan takes the mirror and looks, you can catch a glimpse of her hair and some skin showing. (Original release only.)
When Van Helsing is preparing to render Dracula's crate of soil unusable to the vampire, he is shown breaking a single holy wafer into quarters. When he places them into the soil in the next shot, he actually inserts five quarters, not four.