All other type of items have to work! I never had this happen for a 2 or 3 ingot type of item!
If you had this issue with, let's say a hammer and a great sword, there seems to be a bug about great swords. I think it can happen when you stack them on top of each other (or any buggable item ON a great sword)
It is being worked on already, so for now make sure you do the anvil dragging and are cautious about moving items over items [and watch out for notifications about "you created ********"
if this material does not match, you might have to re-heat the blade and re-craft it into what you want it to be, this fixed a mithryl great blade that was visibly purple but registered as "copper" ... for some reason....
good luck!