This is something that is not publicly confirmed and could be caused by log-editing, bugs or other things. Without a VoD, no confirmation could be made.
Reddit account Acrobatic_Pianist688 posted a thread on Reddit calling attention to a suspicious log of a +23 Nexus Point Xe'nas key. This log has instances of some interesting spells that, according to the log, executed mobs, one of which was a boss at low health and the Reddit post stating that is was a GM that caused it.
We've done some brief investigation into this, and found some interesting tidbits.
Firstly, the Reddit account seems to be a burner account. The account was made 1 year ago, and hasn't posted anything else.
The Log Timestamp and run duration seems to match up with a real run on Raider.io that finished a +23 Nexus Point Xe'nas
It's possible that the log was edited, but this seems unlikely as this seems to be a live log, as there are some untimed Maisara Caverns ahead of it.
Growl (aka Yumytv) interviewed one of the members in the group on Twitch:
His tale of the events appears to confirm that this was a GM that did this.
He says they were all friends except the tank, they think it was a title key for him but not the reset of them, who were all chilling in voice chat with their GM friend
They're doing the key, they kill the boss and realize they're missing percent, and then he "goes to his GM friend and asks, bro can you do us a solid"
