How do you see that it is your opponent that has Forfeited ?Most likely, the Forfeit shown on screen is the system thinking YOU had forfeited (because of the too-often out-of-sync finishing of fights).You see on your device that you finished the 2nd fight, but the connection with the servers glitches out and the system thinks you have crashed/force-closed/other. The Forfeit refers to your side, not your opponent.
Point is that the system thinks that YOU had disconnected/forfeited, even though game played thru for you to the end of that fight on your device. It's been a common problem.
Did you check the match history? If someone forfeits or is disconnected, sometime the system will display the red loser screen even if you won (and vice versa). But the history is always correct, in my experience.