I guess this is the place to post feedback on this? It’s not precisely a quest, and this is not precisely about bugs, so…
This wasn’t a very hard “secret” so I’m not sure this is even really spoiler-y.
Point 1: The item stacks to Unique (10). However, your Idol continues to point out more, and you simply get an error message as if something’s gone wrong. I logged out to try to fix the error so I could keep looting before I realized oh hey, I have all I can have.
Point 2: Again, the item stacks to Unique (10)… but you only need three. All the rest are wasted. You can create multiple quest items for no reason and then you have to delete them because they do nothing.
Since these are not standard quests with clear objectives, there should have been some hint upon picking up the third that maybe you were done, and they should only stack to 3 so you don’t end up with a gob of them you don’t need.