When you hit level 10 (max) with a leader then the next level unlock on the leader select screen will cycle through random unlocks for other leaders.
Edit: Figured out that it's the unlock from the previous leader you looked at that is sticking. If you start the game and choose the level 10 leader first then the next level unlock is empty as expected, but if you look at other leaders and then go back it will cause the unlock from the last one you viewed prior to the level 10 to stick.
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