Presumably the TriStar fleet has now been grounded until all other doors/chutes have been fully checked....???
Without knowing exactly what had been done to the door and slide prior to the attempted deploy that comment is perhaps a bit alarmist. Had there been attempts to remove the slide prior to deciding it was unsafe to do so? What, if anything, had been disconnected? It looks to me like the slide backboard was not connected to the floor, as if the girt bar was not engaged.
Also bear in mind that when evacuation tests are carried out prior to certification that the aircraft must be evacuated in 90 seconds with half the exits inoperative.
Slides do fail to deploy at times, but this one looks to me like it was not deployed correctly, as opposed to any particular failure in the mechanism.