Unable to complete main story quest Rock-solid Protection

Date & Time: 08.03.19, 19:05
Frequency: Continuous
World name: Omega
Character name: Junko Konno
NPC name: Slafborn
Class/Level: White Mage/51
Party or solo: Solo
Area and coordinates: Mor Dhona/Revenant's Toll; x:22.0 y:8.7

Steps:
1. Accepted the quest "Rock-solid Protection" while progressing through the story.
2. Did the Duty "The Sunken Temple of Qarn".
3. Obtained the wardstone and delivered it to Slafborn.
4. After handing over the wardstone, Slafborn tells me to travel to the Sunken Temple of Qarn and obtain a wardstone(same questtext as shown before)
5. Unable to abandon the Quest to try again.
6. Unable to obtain another wardstone from doing The Sunken Temple of Qarn again.
7. Quest shows as completed in the quest log.
8. Logging on and off doesn't do anything.

Please help me, i'd love to further experience the story this game has to offer!
Thank you for your time!