Has anyone had this happen? You're crafting a much-savored item with that UV you've been crafting for weeks to get, and lo and behold, you get another on top of the first.
I'm holding out for it to be a possibility. I would love to get another UV on my expensive CTR bombs...
It will never happen.
When you craft/upgrade your weapon, you're given a chance to keep the existing UV or discard it. When you choose to keep your UV, you will never get a random additional UV on top of it.