After Ronja and Birk have jumped into the stream to hide from the "vildvittror", they head back to their camp and meet Lovis, Ronja's mother.
Lovis remarks that Ronja's hair is wet, but both Ronja's and Birk's clothes are dry.
The castle wall wobbles when Matti throws apples at it.
Big rocks (obviously made of Styrofoam) are bouncing when falling from the cliff wall during Ronja's passage.
When Birk and Ronja are in the woods during the fog and she tells him to keep a rope length's distance, he replies to her but his mouth does not move.
At one part in the film, Birk sneaks over to "Mattisborgen" to meet Ronja in the basement. This is impossible because of the gap between the two castles which is obviously too deep to have a basement below.