I have now gone through the rank up process three times as support. The bar is filled, it is labeled as “Rank Progress: ##%”, the bar says 100%, and yet the next game I play, I’m back to the bottom of the same rank I just “ranked up” from.
For an idea, I’ve been stuck in this infinite loop of staying bronze 1 three rounds now. I fill the bar, win the next game and stay bronze 1, but the bar is now reset. I have photo proof too, as well as my duo experiencing the same thing in real time.