Switching 2 units results in one getting put onto the bench

So basically I was in a game where I had 3 Brawlers and wanted to put in a Volibear for the tier-2 buff. I had also replaced Elise and sold her to put in Swain. In the last second I picked up Swain to put in Voli's place hoping that they would just change places, but the game instead removed my V>olibear from the board and since prep phase was over it automatically put in my most left unit which wasn't Volibear.

SO the issue is that you can't drag a unit that is on the board on top of another one which also is on the board hoping that they would switch. Instead, the one you try to switch gets put on to your bench, potentially resulting in an uncomplete bonus, which can cost you the game, just how it was in my case (I got 3rd place because of this bug).

PLEASE fix this.