Other mistake: Bright realises that the door is unlocked as he pounds on it. The sliding door opens just a little, and the power is off, so it is implied and shown initially that they can be moved by hand. However when they go out of the room and when they go free Sayla and the others, it looks like the door are opening by themselves, not slid open by hand. (00:12:30)
Other mistake: When Scooby is eating the hot dogs at the "Hotus Dogus" stand, his tail goes transparent.