Seen in this clip (minus spaces)
https :// outplayed .tv / world-of-warcraft/ BkOVWW
It appears the lock is stepping down from the ledge when the Null Upheaval finishes, and doesn’t actually hit the Voidstone Fragment, wiping our group. This could potentially happen with the front ledge too (I would think). Please fix, as it cost me my 16 key this week 
It won’t let me send links, or I’d also include the log… I made it public, under jdpriest at warcraftlogs