I have done this quest as various characters. Today as a myth grandmaster, I entered the cave solo, defeated two of the four eels, reentered a second battle with the other two, and defeated them. Then I went to interact with each obelisk there. In the past, after the eels were defeated, I turned each one on and then opened the gate to get the portal piece. Today, after turning each one on, each one went back off. I couldn't get into inner area to get the portal piece.
I then exited the cave and reentered hoping to reset something, but instead all four eels had returned.
I'm very frustrated with this game sometimes for these inexplicable anomolies. This is yet another instance. It doesn't make any sense.
Has anyone else had this experience here? Is there some trick I'm unaware of? I'm beginning to hate the old "just log off and back on and hope it starts to work right again". Some technology!