Guild Wars 2

I am encountering a bug during this quest I did not have before on previous characters and also has not been described on the web. At a certain moment you have to ‘search the area for survivors’. First area is at the ruin outside the caves. When I get here it won’t update, i can not interact with the dead bodies, no undead spawn anymore. Traherne and agent Zrii are still alive so that is not the issue. Went into the cave to the first team but nothing happens anymore (they only mention the attack you have to repel there) . Did this twice, the second time with a guildy but with the same result. I know how this quest works because I did it many times but never encountered this.
Char is a level 71 engineer. Any clue?

Thx for the reply but I stayed several minutes also with my buddy considering all possibilities to continue. he told me that he encountered the other known bugs of this quest in the past but not this one.

Finally managed to do this quest. After restarting it I got to the same point with the same result. The game obviously halted so I went around and killed the remaining foes, got to the first crew and later returned to the area within the ruin. Again nothing happend. ONLY after I climbed the wall at the back – which I suppose is not a normal action – suddenly four undead spawned and the quest continued so i could finish it.