E3S - Sudden Splashing Tsunami spawn and kills everyone

Date & Time: 2019/08/22 - around 10:05PM
Frequency: Once
World name: Zodiark
Character name: Leaping Bear
Monster name: Leviathan (Eden 3 Savage)
Party or solo: Full party
In-game time: 20:05 Server Time
Area and coordinates: E3S
Steps:
1. Engage the Stormy Horizon phase
2. A player gets disconnected during the Plunging Wave phase (?)
3. Everyone dies because a sudden Splashing Tsunami spawns right as a player get disconnected, killing everyone

Please see this Twitch Clip showing the presumed bug : https://clips.twitch.tv/RichCogentSaladTwitchRaid

Not sure if it is a bug or if it is intended for the marker to resolve as soon as a player with the marker disconnects, if that is what has happened: http://forum.square-enix.com/ffxiv/t...=1#post5126835

Not sure why the marker can't just stay where it is for the timer, instead it just explodes instantly.

This is also happening to my group. It's not a proper mechanic that's going off early due to people disconnecting - in the OP the video is long after any debuff mechanics are resolved, and for my group it's happened in many different phases - always after someone disconnects.

As far as we can guess, it's either an anti-cheese mechanic that's going off indiscriminately whenever someone disconnects, regardless of if there's even any mechanics to cheese. Or it's a glitch/bug.

Phases it's happened to us:
After Tsunami, just before the platforms come back (which is long after all debuffs have resolved.)
During first Maelstrom. (Edit: it may have actually been second Maelstrom, I can't remember exactly.)
Immediately as Stormy Horizon phase begins.

Every time it's been when one of our members disconnects.

Edit 2: After more tries, it seems to only happen after Tsunami. Disconnecting at the beginning of the fight before Tsunami doesn't trigger it, but any disconnects later in the fight, after the debuffs have gone out at least once, do.