(at around 18 mins) In the brushes scene, in the kids room, one brush comes out of the red paint can, and the shot after the other brush comes out of the green paint can. The final shot only, showed two brushes with red paint.
(at around 19 mins) When Mark and Jan were sitting on the bed, when Anthony storms in, to beat them. The front view of Mark (on the left) and Jan (on the right) and, when the camera is on Anthony Jan is on the right, and Mark is on the left (back view of the kids).
When Sonny enters the basement, slime drips from the ceiling onto him, as he runs away his shirt is immaculately clean.
(at around 1h 30 mins) When Sonny flies across the room, the string on his back is visible.
After Sonny shoots his mother and she stumbles into the hallway , there are should have been blood and possibly powder burns or blast marks visible on her nightgown , but it is totally clean and undamaged .
Sonny is in his room listening to a Sony Walkman. The movie is set in 1974; the Walkman was not introduced until 1979.
The story is not set in 1974, you can clearly see its set in the early 1980s looking at the cars and the sony walkman wasn't around in 1974 but later in the early 80s.
(at around 33 mins) As Sonny is being chased by something unseen, the camera rises above him, and someone from the crew can be seen standing behind the wall in the bottom left corner.
When Fr. Adamsky tells Patricia Montelli about her behavior at the confessional, this is a breach of the seal of the confession even though they are alone. Even if a confession is face to face, priests are prohibited from speaking about a person's confession outside of the Sacrament of Reconciliation even if it is to the same person.