I am not sure if this is a massive coincidence, but the quality of my teammates is noticeably worse when a challenge to win games is active. I win/lose ~50/50 typically, and rank in the middle of my teams, and then suddenly my teammates are either much worse than usual or those that refuse to play objectives. I will lose 5 games straight and have the highest score on the team each time until I pull off a miracle and singlehandely eke out a win.
Is this just me or does anyone else experience this phenomenon?