Untill you are absolutely sure that you haven't done the kingpin mission "on the same planet, on same character ,in this week", or you'll waste 5 of Bounty hunter Contracts.
I and my friend did the same mistake and wasted 5 contracts yesterday Because we are playing 5+ alts everyday and helping each other's Kingpin ,we lost track which one we have done already. And we know that we can do only one kingpin mission per week on same character (after the GU 2.3.2). We just forgot that.
I think this Unlock system is not bugged but certainly not "fool-proof" neither. It would cause trouble very easily. To avoid this trouble, we must keep track the record when/which/who did the kingpin manually? Too tedious.