Hello, this bug was also reported in the discord 7 days ago, but I decided to post it here too to ensure that it gets acknowledged.
On turn 20, Gengar uses destiny bond. Pelipper uses U-turn out and fails to knock out Gengar.
On turn 21, Annihilape moves first and knocks out Gengar. Gengar did not use any move and fainted. However, the Destiny Bond from turn 20 not take effect to defeat the Annihilape.
Here is the correct outcome of this interaction, where Annihilape should have fainted
https://replay.pokemonshowdown.com/gen9customgame-2493419720