Motherlode final boss drop issue

[Pitach]

WoW Freakz link: https://www.wow-freakz.com/item_finder.php?item=161129&name=mecha-mogul-mk1-remote-activation-device
Character name: Pitach
Bug description: I've been trying to farm all the mats required to assemble the Mecha-Mogul Mk2 mount, for about 3 days now, but the item above, with a drop-rate of 75% doesn't seem to drop. It's supposed to drop on mythic difficulty, but I have tried again and again, on all difficulties, using the engineering Head, and potion, so my engineering skill can be at the maximum possible. I don't know if Blizzard had the same cooldown on dungeons, after you complete a m0 dungeon, you won't be able to loot bosses for another week, but since I have used everything needed for the item to drop, it must've dropped anyway, but it didn't. All the other mats, with a drop-rate between 5 and 2.5% have dropped without a problem.
Proof: https://imgur.com/a/BoQC5Fx

[Lerona]

Confirmed.

https://trello.com/c/rkEsMjwV/459-motherlode-mecha-mogul-mk1-remote-activation-device-dropchance