Defeating Oak with Team?

So, this may be a silly question but, myself and another player were attempting to finish Deal with the Bandits Quest. We got to Oak. Shortly after choosing to kill him, my teammate, a level 27 Ranger, was dead and I was left to fight alone. I beat him after a long while and got the fragment...then continued on. Later, we noticed that his quest to kill Oak had not been completed so we went back, only to find out that I could not help him defeat this highly irritating monster. I was given the option to "kill Oak" but nothing happened when I clicked so I left the area and that's when Oak attacked. After a few attempts trying to kill Oak on his own, he gave up and is unable to complete this quest. Why can I not assist him now? is it because I've already beaten him? Is there no way around this? Glitch? It doesn't seem to make sense that I couldn't help.

Kiya_Lumi

The Bandit quests are slightly bugged, but you can do it by nearly leaving the area, without actually leaving and getting shut out. I think there are some Bandit quest changes in the latest patch that maybe address this issue.

It is best that the person who needs the quest talks to Oak first but does not confirm the kill command until after his helper has spoken to Oak and chosen kill. The helper should be outside the area initially.

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