Not all dumb training exercises relate to CB's or system failures. In the late 80's during an AEP session, it was decided that all attendees would go to the adjacent hangar as on of our 737's was undergoing a significant check and the R2 door slide was to be deployed as a routine procedure. So much was made of the deployment onto the hangar floor and then all to go down the slide. Of the 6 pilots and 14 cabin crew there were 4 injuries. Several CC injured their backs and one Captain broke both wrists and was off work for a couple of months. He sued the company successfully for the humiliation of having someone else wipe his backside for many weeks.
I understand an American crew member unnecessarily died after bouncing off a slide from the top deck of a 747 during training.