I got this behaviour with any audio output: analog outs (I only tried pair I) , headphones as well as USB audio.
Doing some test I believe the affected sounds/patches are all vocoder related ? No input signal is attached. Filters seem to be disabled. A little
reverb or changing the first oscillator to any other type will make both channels hearable, but Signal starts fading and stays on the right again after about 15 secs (???)
Enabling delay has no effect, but changing chorus to rotary will make the signal audible on both channels permanently.
Is this perhaps normal for vocoder patches ? I was reading a post somewhere that vocoder patches split stereo channels for orginal/processed Input signals.
*Edit*
Ok, i tested with Factory ROM-U 76 "VOC osc 1":
If there is an Input signal this patch sounds quite normal "vocodish" on both stereo channels with normal volume and no recognizable difference between channels.
With inputs plugged but no signal (played over MIDI (USB as well as MIDI IN)) I got a significant louder signal only on one Stereo channel.
Im not sure about this… is that normal and only sounds weird missing any input Signal or does my machine behave wrong ?