When Peter Lorre enters the residence and starts breaking pots,looking for money, one of the pots has a round base and is fluted. The pot hitting the floor, near the cat, is a little different color grey and more cylindrical.
There is a Spider, motionless, shown on a glass, then there is a shot of the spider moving, in the next shot, the spider is in the same position as it was before.
Lenora's hair changes between shots constantly through the tale.
Locke's position in the chair changes between two continuous shots.
Like in all older movies, there a lot of discontinuity throughout the scenes .
In the Black Cat tale, after the police knock open the wall and shows close up of Annabel and the cat, you can she her chest move as she exhales a breath.
When Montresor is asleep and falls from the chair on the floor, he uses hands to protect him from the fall, revealing the act. He also blinks once.
Ernest is still breathing after being dead and rotten.
Annabel is still breathing when we see her dead.
When Morella takes control of Lenora's body, as Vincent Price walks up the last time before the reveal, you can see a red backstage light in the "window."
Carmichael says if Dr. James kills him, M. Valdemar will never be released, but Dr. James could threaten to injure Carmichael so as to cause great pain without killing him to force him to release M. Valdemar.