First, your replay doesnt work, it just immediately surrenders, so I think you have the wrong code.
Second, if youre trying to activate the fusion effect in the same chain that youre activating Eternal Favorite, you cannot, which is not a bug.
As per Eternal Favorite’s rulings (Card Database) you cannot activate the fusion summon effect of Eternal Favorite in the same chain as you activate Eternal Favorite, because the cost requires sending “this face-up card to the GY”, and until the chain where you activate the card resolves, Eternal Favorite is not considered a face-up card yet.
This previously worked because it was a bug that hadn’t been noticed, but now works as per the rulings.