Plot hole: Tahnee was sent to boarding school when she got fired as a way to get her out of the show, but she was 17 and so isn't that a bit of a silly way to write her out? In Melbourne Australia, you can leave school if you wish at 15, so she in theory shouldn't be able to be forced into going to Boarding School.
Continuity mistake: When Anne and Evert are driving toward the Norwegian/Swedish border, Anne pulls back the rug in the back of the sled, and discovers the dead Bjørn. He is then flat on his back, staring upwards. Moments later, when the Swedish border guards pull back the rug to look at the corpse, he is face down. No one touched him, and the sled did not bump enough to roll the body completely over.
Other mistake: Mutt reads the card about the "fatal fluffies." He says "I'm sure you'll enjoy their deadly secrets", but the card reads "I'm sure you'll enjoy their amazing "split" personalities."
Continuity mistake: Episode 2x15, "Witness for the Execution": When David and Maddie are debating whether or not to help Lawrence Everett, the towel David uses to wipe shaving cream off his face jumps around during the scene. It's around his neck, then in his hands, then on his shoulder, and back in his hands, etc. (00:15:40)