Almost exactly the same thing happened to me. I had a netherite sword with no custom name and no fire aspect (though the other enchantments were exactly the same), and there wasn't any sort of mob on the other side. I was able to reproduce the bug several times afterwards by throwing blocks at the inside of the portal frame while waiting for it to send me through. I was on a realm if that changes anything.
Jonathan Noah Scott
Almost exactly the same thing happened to me. I had a netherite sword with no custom name and no fire aspect (though the other enchantments were exactly the same), and there wasn't any sort of mob on the other side. I was able to reproduce the bug several times afterwards by throwing blocks at the inside of the portal frame while waiting for it to send me through. I was on a realm if that changes anything.