I have other promethium gear that repairs with no problems, but no matter how long the katana is in my active hand, it will not regain any durability. I haven't yet tested this with any other modded weapons (i don't have that much promethium, lol), so I'm not sure if this problem is isolated to the katana or not.
I am not sure if this bug is caused by something in Simply Swords or Mythic Metals, so I am opening this issue under both.

What version of Simply Swords are you using?

What version of Simply Swords are you using?

1.54.0-1.20.1

Mythic metals got updated on 1.20.1, reworking prometheum code, this mod might require an update too for it to work properly