Stupidity: Henshaw knocks out Duffer and handcuffs him to the steering wheel in order to go in alone and save the women, but this highly-trained agent somehow doesn't think to take Duffer's radio, meaning of course, as soon as he wakes up he can call to have the place blown up as he was going to before.
Stupidity: During the ghost chase montage, why would Velma look for her glasses with her hand in midair instead than on the ground? No matter how nearsighted you are, the closest wall, or obstacle, is meters away and you'll never find your glasses anywhere but the floor. She does it for a longer time than anyone would. (00:52:40)