I completed the Glowecestrescire quest line so I went back to get all of the Mysteries, Wealth, and Artifacts. When completing out Devil's Quoits it was not checking off the mystery or removing it from the map to show it had been completed. I tried restarting client, loading an older save, and even tried completing it while commanding/not commanding the small boat; all failed. The workaround I finally was able to use to get it completed was by using the longship and standing on the far side while having it parallel to the shore

@ubiwan didn't work. I have 1 opal no matter what save I load. When I saved and logged out last night I had somewhere around 160