Opponent had one Amalia Benavides Aguirre, two Siege Veteran, one Dunland Crebain, and a handful of tokens on the field. They had 14 life. They had Virtue of Persistence and Banishing Slash in hand (my Invasion of Gobakhan let me see their hand).

I had Oracle of the Nine, Troublemaker Ouphe, Haywire Mite, Proft's Eidetic Memory, and Invasion of Gobakhan on the field.

Opponent used Virtue of Persistence to give my Oracle of the Nine -3/-3 until end of turn and it died. Amalia Benavides Aguirre ability activated after the Oracle died.

This is specifically a "Whenever you gain life" effect. The opponent was at 14 life both before and after the Oracle died, and there was nothing in play to gain life.

Not sure why the Amalia activated, but there was no reason for it to activate. It did add a counter and give it 1 toughness higher than I was able to kill it, allowing opponent to attack where they otherwise would not have, like previous turns.

Ultimately, it did not matter in this particular game. I got horrible draws and it was an inevitable loss. However, it is a bug nonetheless, and could potentially change outcomes of other games if it can activate incorrectly.

Attached log, and screenshot of all cards and the board state, from the start of my turn after the Oracle died. Was, unfortunately, not recording this time so I only have a screenshot, not a video.