Continuity mistake: At the beginning, after aunt Zelda casts a spell to prevent Sabrina conjuring pancake batter, no sparks or noises come out from her fingers.
Suggested correction: 95% of the time nothing comes out of her finger.
Nobody Nose Libby Like Sabrina Nose Libby - S3-E9
Other mistake: After Salem and Sabrina are shrunk down into the toy plane you see the kitchen from inside the cockpit, but when they are shrunk down to be tiny enough to go into Libby's nose, the view from inside the cockpit is the same as it was before they were shrunk down even further. Since they are that much smaller everything should be seen as much bigger.
Continuity mistake: When Sabrina comes back from dream dropping on Harvey, there is a picture of her on her family secret board. Later after her aunts try to get her to solve the family secret, she says she got a new clue. It was the picture of her and she hung it on her board.