Anyway, it reads like Nyrstar applied for the tender, got knocked back and then filed an arbitration request (plan B) to get what it was after after an aledged few months of discussions prior to tender approval.
It’s quite possible that it wasn’t mentioned in the DD as stated by NCR and Nyrstar may have thought they’ve found a loophole.
Either way it seems for now, to me anyway that this is just, as stated; an opportunistic clutch at straws by Nyrstar who’ve decided they want back in after finding out that there’s zinc in them thar tailings and someone’s gonna extract it.