The same thing happened for me. That cable was by far the shortest and a slight pull of the display up caused the connector to come free. Luckily it wasn't damaged by this. It was pretty unclear to me how that connector fit in as well. It slides in and out parallel to the surface of the mother board, up towards the top of the iMac to unplug and down towards the bottom to plug in. I agree, if I were to do this repair again that is the first interior cable I would disconnect. Maybe a closeup of the cable plugged in and unplugged to show exactly how it engages and disengages would be good as well.