Cannot to see Kaz'tik the Manipulator

I’ve reorganized my experience in the hopes of describing the problem I encountered a bit better.

There are two “By the Sea, Nevermore” quests, the one with ID 31682 is provided by Zer’ik(ID 65975), and the one with ID 31089 is provided by Kor’ik(ID 65365). If you kill Kor’ik during the quest “Corruption Runs Deep”(ID 31441), then Zer’ik will replace him at Amberglow Hollow and provide the following quests.

Sorry for doing the following steps because I am a perfectionist:

  1. I killed Kor’ik, and then completed quests “Better With Age”(ID 31681), “Crime and Punishment”(ID 31680) and “By the Sea, Nevermore”(ID 31682) provided by Zer’ik.
  2. I successfully saw “Kaz’tik the Manipulator” and received quest “Reunited”(ID 31091).
  3. At this point I party synced with my WOW2 character, and completed quests “Better With Age”(ID 31090) and “Crime and Punishment”(ID 31088) provided by Kor’ik without killing him.
  4. Then I received quest “By the Sea, Nevermore”(ID 31089) provided by Kor’ik, but this time I couldn’t wake Kaz’tik the Manipulator up again.
  5. Through this message:
    Legacy bugs (V 3.0)
    Player’s comment says:
    Name: By the Sea, Nevermore
    ID: 31682
    Issue: if you are playing through this quest with a friend in party sync, you will always get stuck on this quest, nearest we could tell is that the boulder you are supposed to interact with has a tracking quest that currently cannot be replayed, so the game thinks the boulder is gone but you still need credit for destroying it + the NPC doesnt spawn.

I left the team and tried to use the quest item “Klaxxi Tuning Fork” (ID: 84119) to awake Kaz’tik the Manipulator in the rock but nothing happened and the quest could not be completed.
6. I gave up the quest “By the Sea, Nevermore”(ID 31089), the rock disappeared, but Kaz’tik the Manipulator did not spawn anywhere in (41.6,72), (43.4,63.4) or (54.2,35.8).
7. I want to re-accept this quest, but neither Zer’ik nor Kor’ik are at Amberglow Hollow anymore. The query found that I need to complete the quest “By the Sea, Nevermore”(ID 31089) to see Kaz’tik the Manipulator and continue the following quests, but in fact I have killed Kor’ik and it is impossible to receive this quest by him again.

Through these messages:

Player’s comment says:
I have the same issue, my quest log was too full and got rid of it, then came back to take it again, and no way to have the npc or the quest T.T

I created a new character to try to complete these quest lines again, but encountered the same problem again.