Azure Beastbinder second part not working sometimes

stikxs

When this guy attacks and there are no opposing supports he's supposed to kill an opposing creature, however sometimes that doesn't happen. Noticed it a lot in this past Break the Powerstone event. I believe the problem comes from the opponent having an indestructible support, this guy trying to destroy it and failing and nothing happens. In the event he did work correctly for me (killing opposing creatures when no supports are present) before the first event support went away and both players get indestructible ones. Once the indestructible supports came out he would no longer kill any creatures.