[Mechagon Rare] Boggac Skullbasher not Spawned

[Koler]

WoW Freakz link: https://www.wow-freakz.com/npc_finder.php?npc=151308&&name=boggac-skullbash
Bug description: Boggac Skullbash is never visible on the server. In theory he should spawn after killing troggs on Mechagon, but he never do this.
This is the only rare mob, which is not working from Rest In Pistons achievment, which is required for Mecha-Done.
Proof: https://i.imgur.com/E021jJY.jpg