I faced "error : bad server response" a lot recently (maybe these last 1 week) when i play using android.
Sometimes it happens when i open status menu. Sometimes when i challenge qm, and when this happen i cant enter qm although my ign are "considered" playing in screen vs somebody. When click qm again, the classic message "you already have game progressing.... " appear. Then my rating will drop since i will lose automatically.
And sometimes i faced this bad server response in my victory/defeat screen after i win/lose game, the result is i dont get any exp/rating/score.

really this is very frustrating... did someone have the same problem like mine?