Paladin class quest "Poisoned Hearts" Bug

Hello,
I discovered a bug with the level 45 Paladin class quest "Poisoned Hearts" in Southern Thanalan.
The goal of the Quest is to open 4 coffers to get your class equip.
At each location spawn 2 NPCs that you have to kill in order to be able to open the coffer.
One of the coffers is bugged and cant be opened after killing the NPCs, this does not only seem to be the case for me since I met other players on that quest there who had the same problem.
The bugged coffer is the one furthest in the north.
My Server is Lich.

I already tried logging off and on again, switching class and changing location and coming back.

Also the Ingame Support told me there is nothing they can do about it, which annoys me. I had contact with the Ingame Support of many other mmorpgs and helping with bugged quests is something all of them could help with.

Greetings Devastor,

We thank you for posting your concerns regarding "Poisoned Hearts". I have made sure to submit all of your information to the development team and they will thoroughly investigate this matter based on your report. Unfortunately, I cannot guarantee that a direct response will be posted on this thread, but I do recommend checking Here or Here for any details regarding the development team's investigation.

Thanks for your report!

- Furlamseere