Blackened used to happen if you really borked an enchant (cursed and like a neg 2x enchant or something rough) it could then be uncursed and enchanted back up with no addition issues other than having to put it all back together. A friend of mine is swinging my old perfect blackened vultite falchion. Also could probably be an alter. Unless the material itself is something strange, you should be good.
I don't know much about enchanting, but could it be a bless getting in the way?
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