*edit
So i found out a workaround for this issue if it’s stuck on your server. may fix it for the server but i can confirm that it fixes it for you.
If the quest is stuck at 2/3 for you and everything is green. do the following.
1. Go back outside of the cave and follow that path on the rocks. Now pay attention to the shore VERY close to the water, there will be one shark can that be targeted through the rock (don’t know why it’s there but it is). It should be red and you should be able to kill it.
Voila and your quest is complete until they find a fix for it.
Now if you do this and you still don’t get it then I dunno what to say =(
*edit (again)
after the server rollback, the shark wasn’t in the rock anymore so it may be fixed. not 100% sure. (as in it may break again)
