When both players control The Bloodbile Swarm from YFRA, if I sacrifice a creature during my opponent's turn, both Swarm triggers go on the stack and resolve in Active Player/Non-active player order, which correctly means my trigger resolves first and exiled the creature for me to cast later. My opponent's trigger fizzles.

However, if I discard (as opposed to sacrificed) a creature card during my opponent's turn, both triggers go on the stack, mine resolves first, and the card is exiled for me to cast later. BUT, then my opponent's trigger resolves and moves the now exiled card to their castable zone and makes it so that I cannot cast it. I believe this scenario is a bug.