Left the game after that timer starts after someone leaves but still lost rank percentage (/SR) twice.
Even if you have a leaver, you still take the same SR drop for losing a game.
By twice do you mean it was a big drop? Or you have two lost/abandoned games in your history for the one played? Did you get timed out of comp?
There used to be a bug about leaving once the the timer ran out when it was supposed to be fine and still getting a “leaver” penalty for it including extra SR lost. I’ve always had the (unfounded) suspicion it could still be around in some form but I don’t see many reports related to it.