After sneaking behind Minthara and the other Goblin we decided to destroy the Wardrums first.
Unfortunately the Goblin is still running through us and drumming joyful in the air where the Drums were before, triggering the other Goblins hostile.
As well it is possible to start the Dialog with Minthara to keep her stuck, then destroy the Wardrums triggering a fight with the Goblin, kill him first and afterwards start the fight with Minthara.
