During my live, the sound from the desktop just disappears, just the sound of my voice and my microphone. normally after 1 hour of live it happens
Have you checked the sound drivers for any update? Updates will fix some of the errors that you may encounter.
Did you check your ports of your audio device? What audio device are you using on your desktop? your cords or your setup might affect some audio interference.
You can verify this on XSplit Gamecaster’s Devices Settings if your system audio is getting any signal.