Hello,
Not sure if it’s the same on PC as on PS5 but when you try to use a rune that is marked as favorite, either by crafting or converting runes, the system show a Warning message but the message itself has coding error, since it’s not actually showing the warning message but the variable used in the code.
The message shown is :
!!Missing!! - 270735:CraftUsingFavoritedItemsWarning
https://i.imgur.com/1yZxhr3.png