A bug has been discovered on Mythic Tindral which causes him to fly faster in the Intermission, likely wiping your raid if it happens.
A rare bug has been discovered on Mythic Tindral which causes him to fly faster in the Intermission, allowing him to arrive at the platform 8 seconds ahead of time. This also allows him to start his Supernova cast 8 seconds earlier, likely wiping your group.
You can see this in this clip:
As sleuthed by Draco and other members of the Raid Leader Exchange discord, it seems that the Witherrot Tome item might be the one causing the bug.
This Embellishment is not frequently crafted and only really by a subset of the Elemental Shaman community. Elemental Shaman isn't meta this tier and isn't being played much, and then a rare Embellishment means that this item really isn't seem often in Mythic raid this tier.
Two guilds reported having this fast flying Tindral issue, and both were running Elemental Shamans with the Witherrot Tome. When one of the guilds swapped off the Elemental Shaman, Tindral returned back to normal. No guild has a public log on Warcraft Logs with a Witherrot Tome at the moment, making many people think this is the cause.
Looking at the spell data Tome-Wrought Rot, it looks like Effect #2 is missing a minus sign and the text «Snared», meaning that it likely can apply to bosses. Then there might be a bug where Tindral is supposed to not be slowed, so it compensates for the 30% slow with +30% movement speed, then when the Tome effect wears off, Tindral zooms ahead. Hopefully Blizzard fixes this soon!