Revealing mistake: After Lansbury makes her clothes start to move, her nightgown attacks someone and you can notice the strings that make the gown move.
Plot hole: When Miss Price, Professor Browne and the children return from their magical journey to the island of Naboombu and realize they no longer have the Star of Astroroth pendant, Miss Price says, "I should have known it would be quite impossible to take an object from one world into another." Yet, they had no problem taking themselves, the bed, blankets and pillows from one world into another.
Audio problem: When Professor Brown and Miss Price are eating, he asks, "Why are you so interested in that?" His mouth doesn't move in sync with the words.
Character mistake: The closing shot of a newspaper article shows the word "rumor", film is set in England where it's spelled "rumour".
Deliberate mistake: During Lansbury and Dr. Brown's dance scene under the water, the drawings behind them (with couples of fishes sitting on their seats) are a still drawing, no animation at all.
Sacha
Continuity mistake: One of Mr. Browne's apples falls on the gravy when he is juggling, splashing his face and shirt. Later his shirt is spotless.
Sacha Continuity mistake: After trying to fly on her broom, Ms Price face plants on the floor, but a frame later, from a different angle, she is laying sideways.
Sacha Continuity mistake: At the library, Mr. Brown swaps from leaning on the center of a shelf, by the right of a column, to leaning on the center of the column.
Sacha Revealing mistake: When Ms Price plummets on her broom, a wire attached to her waist is visible.
Sacha Visible crew/equipment: When Ms Price tries to fly on her broom and she is launched upwards and wipes-out on the floor, she is replaced by a very obvious and much younger stunt double.
Sacha Continuity mistake: When Lansbury and Dr. Brown finish dancing, there's a wide shot of Lansbury giving a very small step forward to finish the dance. A second later, in a closer shot of her face, she moves as if she was repeating that very same movement.
Sacha 
Continuity mistake: At the lagoon, after Price and Brown win the cup and the hook falls, Paul is suddenly replaced with a completely different kid, older and much taller.
Sacha Audio problem: During the Germans' attack, Price is on her broom and tells Brown to protect the kids. Bullet traces fly next to her, but no sound is heard. Then it cuts to a shot of the Germans loading and firing, and now the bangs are head.
Sacha 
Continuity mistake: When the lion king blows the soccer ball into the goal, the ball disappears in the following wide angle.
Sacha Continuity mistake: The green skirt that comes alive smacks Ms. Price's nape and sends her glasses to the tip of her nose. In the following angle they are perfectly placed.
Sacha Revealing mistake: When the white gown enters Ms. Price's house, before it starts dancing with Prof. Brown, a string holding it is visible.
Sacha Visible crew/equipment: At the end of the film, taking place in a sunny field, Paul holds the bedknob and in both of the final shots about 3 or 4 lighting screens are reflected.
Sacha Revealing mistake: When Ms. Price starts to make the shoes move, the strings attached are visible.
Sacha Continuity mistake: When the soccer match ends, the lion king rests on the goal and you can see the damages done. In the immediate wide angle, the goalie has totally different damages.
Sacha Continuity mistake: Before Ms. Price makes the army move, she grabs her broom and the position and shape of the handkerchief on her blouse differs between the first and the angle following.
Sacha 
Answer: All I could catch was "VORAN,VORAN" which means "Go, go!"