A similar issue happened to me just now, and my partner several days ago. I was playing Elise and I was shown to be in the top 3. but kept playing Akazamzarak. Sky Captain was in first place but had only completed one battle the whole game, was only on tier 1. After beating Akazamzarak after several rounds straight, I came in second, and lost the achievement for the Elise first place win.
My Fiancee several days ago had the exact same situation, though i’m unsure which hero she was playing.
Just happened to me too, about a few minutes ago. Fought the third place guy like 5 rounds in a row and finally won, really close, and then the game ended and said 2nd place. Cheated me out of a first place 
didn’t know this was a common bug, I hope they resolve it soon
Spread awareness to get rid of these hackers
I got the same bug like this 10 to 15 times now, this is really annoying
Just happened to me! Quite discouraging and with bugs as such makes the game unplayable. This has been reported for MONTHS… since at least July 2020. Blizzard has far too many resources for a bug as such to exist for so long. Bad management of development.
This bug makes it hard to stick with Battlegrounds for me. Takes a lot for me to get 1st, only to have some stupid hack take it away.