So recently my rank reset to Bronze 10 from a Gold 8 game which I won. My friend in Silver also got reverted to Bronze 10 out of nowhere. We were playing in standard and did not switch mode at all.
This doesn’t sound like a bug. It’s the first of the month, so it’s ranked reset day.
Today is the first of the month, reset day for ladder, so it’s intentional for everyone to have their ranks reset. If you were playing at the time it occurred, it happens seamlessly and might appear abruptly, but I’m sure the next time you log in and you receive your monthly rewards it will become apparent as to what has happened.
Had a similar thing happen. After the ranks were reset I won a few games and as of just checking in back to bronze 9. I was gold 5 before the reset and should be receiving 4 bonus stars each win, but now I only recieve 2.