Because I have less than 3 team-ups available I am unable to get rid of boost used in last fight. There is no unselect option I am forced to continue using boosts until I have 3 team-ups available again.
Which means you never use any of your last 3 team-ups or you will can get stuck like this.
This decision made more sense when TUs weren’t implemented and the boost screen always came up before a fight: “remove” was right there in front of you every time. Since the addition of TU powers, boosts are something of a red-headed stepchild.