Other mistake: If the Maitlands cannot be seen in a reflection being ghosts, then Lydia would not have seen them in the attic window in her camera, as that uses a mirror to reflect the image through the viewfinder.
Suggested correction: However, when Lydia moves the camera away from her face to get a better look, she had both eyes open when using the camera (with her right eye looking through the viewfinder). This is a recommended technique to help get a perspective and keep one's focus on the subject. This means she could have seen the Maitlands with her left eye, the one that had a direct view of the window.
This is not how the scene plays out. She first supposedly spots them while looking through her camera, which then causes her to take a better look with the camera away from her face. She would have no reason to do that if she didn't see them in the camera, which, as we know, would not be possible given they do not cast a reflection for the mirror in the camera for Lydia to see.
Or, she just saw the curtain move and thought that was odd, then moved the camera from her face and realised there were 2 faces there. There is no indication at all that she saw them straight away.
A curtain moving from an open window is not odd. You're really reaching here, and her reaction indicates she saw far more than a curtain moving. She literally stops in her tracks and dramatically lowers the camera - the same camera that she had to her face she was looking through. Anyone who has used an SLR camera does not use two eyes open, as it is nearly impossible to focus and see things, given one eye would be zoomed in and the other would be unaided.
Continuity mistake: When the wedding clothes are laid out for the seance, there are no pants/trousers in place for Adam, but when he materialises he has them on.
Continuity mistake: In the Day O scene. Lydia is sitting at the table next to her father. When the possession takes place, Lydia is not longer at the table and in a brief moment is seen in the corner hiding, laughing behind her chair. The camera closes in on the song and dance, and when pulls it back Lydia and her chair are gone and the corner is empty.
Visible crew/equipment: There is a unknown 3rd person helping Charles and Otho remove the model from the attic. You can see him briefly just as the scene ends on the left side of the screen moving the front portion of the model, closest to the camera, between us and Charles. Charles and Otho would be hard put to move that entire model by themselves. Otho says it is sectional, but they still seem to move the entire model in one piece.
Continuity mistake: Adam picks up his head from the table and puts it back on. In the following shots the blood around the neck and head has disappeared.
Continuity mistake: At the start, when Adam drives to the store a fireman is cleaning the right side of the fire truck. A shot later he's now cleaning the front part. Also, when he exits the store the two firemen swap places between shots.
Continuity mistake: As Barbara recoils after getting hit with the steel plate over her mouth, she starts to move back just before, and repeats the move just after, it appears.
Continuity mistake: When Beetlejuice is screaming at Barbara and Adam, he kicks over the model tree. As he does, his hands are close to his sides. In the closer shot, they're a bit further out from his sides in preparation of the crotch grabbing joke.
