Ok, this is a weird one, but I think I have it figured out.
So, the bug is that whenever you make a short blade (single ingot blade), regardless of the ingot you used, the final blade will be of whatever material the last thing you crafted was.
I.e. If I were to make a titanium sword, then I bought a copper ingot, heated it up, and hit it on the anvil, then I would get a titanium short blade.
This works both going up the tiers of metal and going down, so I have to make a titanium (enter weapon here) before I can make either a bladed polearm or a dagger.