When Hielke and Sietse tie the boat to one of the poles at a wharf before meeting Gerben, flowers are visible next to the pole. Later, when they detach the boat from the wharf, both the flowers and the pole are gone.
The colours of the t-shirts that Hielke and Sietse are wearing underneath their overalls change various times.
When Hielke, Sietse and Kees are standing behind Bob while he is dressing, the distance between them is less than five seconds. When they decide to attack and the gang runs away, it takes more than 10 seconds before they finally reach them.
Multiple shots are made with different weather occasions, like sunset or at dawn with a foggy sky, while the movie makes the audience believe everything happens in just 2 days.
When Kees leaves the candy-store, the owner stays in the doorway. Kees then comes out of an alley, runs around the corner, jumps in the boat and sails away, waving at the screaming owner. But it's impossible that the owner can see Kees from the doorstep with so many turns.