Tandem Takedown not working as worded [Investigating]

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TheHunter
TheHunter Posts: 282 Mover and Shaker

The first part worked - my creatures got a +1/+0 buff as expected.
I wanted the second part to damage my own creature to meet an objective. Greg had no Vanguards in play but I wasn't asked to pick a target and instead the combat phase started. As worded, I should have been able to target one of my three creatures.