Errors made by characters (possibly deliberate errors by the filmmakers): Devon refers to Baba Yaga as "he" several times and describes the character as having chicken legs, however, in Russian faerie tales/folklore Baba Yaga is an old woman and gets around by flying in a mortar and pestle, it is her house that runs about on chicken legs.
Continuity: When Devon pours a glass of water for Trent it is less than half full. In the next scene outside it is seen to be more than half full even after splashing it about.