I've noticed this for the last two dwarves that have gone fey on me... odd little bug that i've been able to trigger as far as I can tell. So I had a dwarf go fey, and I was curious as to what the dwarf would want for their construction. Dwarf took over workshop, and went to grab the first item. Walked back to the workshop and right as he got back I hit Q to look at what was needed as the dwarf was standing there.... list seemed to lag a bit, before scrolling through a list of 6 or 7 more things the dwarf wanted. I watched it scroll for a bit before hitting space to unpause....whereupon the dwarf immediately began construction.
....ok....
So the dwarf makes a slate bracelet. That's it. Only slate. Ignored the other items he wanted. Odd, but ok. Figured i'd wait to see what happened with the next dwarf that went fey, to see if I could repeat it.
So the next dwarf that goes fey is a child, and this child decides it wants to take over my craftsdwarf workshop. Goes to grab some kobold bones and comes back to the workshop, whereupon I hit q again to see what she wanted. Many different things scroll by, such as skeletons and cloth and all manner of different things. Again, I wait a bit and then unpause, to see what happens. This time she went and got one more thing on the list, before starting the contstruction. I'm now left with a kobold bone cage with Obsidian spikes, and that's it.
So this leaves me to wonder...is q'ing the workshop while they're still in the process of gathering materials somehow breaking the list of otherwise needed materials? It's certainly something to look into, as i've had it happen twice now. Sure, it's nice to keep your dwarves sane if you don't have what you need for 'em, but at the same time you could have a much nicer artifact if you DO have what they want.