There was a great line by the great Capt Warren Vanderburgh that applies to this incident. "I'm so sorry, I didn't mean to make you like this". This incident with a warrior door comming open and the instruct not being able to deal with it adequitely is a classic example of what happens when generations of instructor who just don't know are teaching new instructors sho just don't know, then they go on to teach others.
I have done probably 500 landings with doors floating open on the Warrior. How do I know this, I have sent at least 500 1st solos in Warriors, and everyone has had the door pop open on the 1st circuit (while dual), because I made it happen. The students freaks out , I show them the aircraft flies quite fine, they calm down when they realise the thing is not going to fall out of the sky, we land, close the door and continue the sortie. I have had dozens and dozens of students have the door pop open on later flights and they all said they were well prepared from the experiance with me and just got on with flying the aircraft. No biggie.
I place the blame squarely on that instructors own previous instructors, the chief pilot who did the induction of the instructor (S&P checks), the instructors who sent her first solo, PP:, CPL training and more importantly, the instructors who did her instructor rating and the examiner who tested her for the rating. All share a portion of the blame.