The great works interface in Civ 6 is so very, very kludgy to begin with, especially when trying to move works from site to site (sometimes it tells me I can't move one when, in fact, I can), but the thing that's driving me the most crazy is that when I want to trade works with other leaders, I can't even select any work that's not a great work of writing. I have to assume this is a bug, because I can't for the life of me imagine why the developers would make this discrepancy an intentional part of the game. On an unrelated note, about five games out of six, Civ 6 decides that every artifact I dig up is "ancient" for theming purposes, even if it dates to another era. This is helpful but almost certainly not the way the game is supposed to work. Even more perplexingly, about one game out of six, it dates them correctly!