Well, there have been quite a few system updates over the last two months (since I last used used FS-UAE), so I can't pinpoint a change. It's the only thing not generating audio output now though. I thought the "restarting audio stream 0 (buffer underrun)" looked suspicious.
Pressing F12 shows that the volume is full also...
Also tried rebooting, disabling other appliactions that might be hogging the audio before starting FS-UAE. Still no luck.
<edit>While doing something completely unrelated (ferrying kids on and off a bouncy castle at a party), I remembered editing the pulseaudio config file recently in an attempt to mix my stereo to mono/joint stereo. I undid my change and now FS-UAE runs fine. I never thought of it because everything else worked after making the change. Apologies - I think I should donate everytime I make a stupid bug report
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