I'm trying to do the item collection quests Not a Weapon to Spare and Flowers for a Lady in Thinglad. I've been able to collect some of the flashing items but not all, in some instances i can't even click on the glowing sparkly item - hovering over them doesn't show the icon that tells you the item is collectable. So yeah, in one instance the flower for flowers of the lady spawned within a group of tall plants and I was unable to collect that particular flower because hovering over it didn't even show the icon that says you can pick this up.
I don't know if this has changed with 12.3 (I was in Thinglad only in January and didn't run into this issue) or if it is affecting especially you. But I would suggest that you try to click on the name of the item.
The broken channel fountains in the basement of Thorin's hall have been inaccessible for my characters I don't know how long. Clicking on the *name* of the ruptures yet allows for *using* them properly. The same happened to my lore master in Wildermore, he was told to burn invisible Orc corpses outside Forlaw. Clicking on the names worked.