Problem with mic outputs on RX3

Last night I suddenly had problems with the two mic outputs: a saxophone on one and the mic on the other. At the beginning of the party, everything was fine, but later on the two stopped working almost completely; you had to turn the volume up very high to hear anything, and even then it sounded distorted. Strangely enough, I could hear the sax just fine through my headphones on the master cue...

Any ideas about what the problem could be?

Kind regards,
Danjo