Trainer Brain
There are a lot of new CSM's in the Perth base...... My guess is they've been in the trainer doing EPS and their muscle memory is opening the door to perform an evacuation.
We're trained when disarming to remove the pin from the pouch FIRST, so it's in your hand and THEN disarm. Not the other way around. That way if you forget to disarm then you're holding the pin and that will trigger the action.
We're also trained to never, ever open the door..... Always ground staff.
Hence me thinking it must have been a muscle memory thing.