EDIT: After reloading I can repair the item as expected.
My pally “Turk” made a Steel runeword scimitar and cannot repair it at Charsi. PTR hardcore ladder.
I believe the base was superior, +1 damage. Have sufficient gold but using either the “repair all equipment” button or manually using the “repair” button and clicking on the Steel gives the popup “I cannot complete that request”. Is repeatable.
Mouse pointer doesn’t show up in screenshots but obviously it was over the scimitar.