Any error messages in the system log?
The problem is that i couldn't find any significant errors. All i was able to gather is:
journalctl: апр 13 13:47:56 ArchLinux pulseaudio[2115]: [pulseaudio] pid.c: Daemon already running. апр 13 13:48:03 ArchLinux pulseaudio[2098]: [alsa-sink-DICE] alsa-sink.c: ALSA woke us up to write new data to the device, but there was actually nothing to write! апр 13 13:48:03 ArchLinux pulseaudio[2098]: [alsa-sink-DICE] alsa-sink.c: Most likely this is a bug in the ALSA driver 'snd_dice'. Please report this issue to the ALSA developers. апр 13 13:48:03 ArchLinux pulseaudio[2098]: [alsa-sink-DICE] alsa-sink.c: We were woken up with POLLOUT set -- however a subsequent snd_pcm_avail() returned 0 or another value < min_avail.
Sometimes see this: май 03 17:30:27 ArchLinux pulseaudio[657]: [alsa-sink-DICE] alsa-sink.c: Resume failed, couldn't restore original sample settings.
Sometimes after play failed i see in sysnotification area: "DesktopKonnect6 don't work, 'Default' will be used"
In dmesg i see no errors.
What exactly happens when it cannot play sound?
No errors. It's just don't play anything. For example, for video, various players handle it differently - some are just play video without any sound, some can't play video at all(stops play on first frame).
What exactly happens when it "breaks"?
Almost nothing, sometimes i can hear that music breaks with some kind of "click-sound", like someone pulled the wire from my loudspeakers. But this sound is barely noticeable. If i try to play file again i hear some kind of "initialization sound", like when device open on PC boot. It's hard to describe it in my English :)
If you send me info about how to gather more detailed logs, i try do this. P.S. Sorry for long time to answer.