Perhaps you have a similar situation to mine - my laptop has two sound outputs, hdmi and analogue.
Most of the time hdmi comes up as the default sound output, but not always.
If hdmi comes up as the default, neither hdmi nor analogue will work unless the graphics-KERNEL extension is loaded before any sound drivers.
In order for hdmi to work properly, the alsa-config extension needs to be loaded after graphics-KERNEL and before the alsa extension.
Although they add bloat, pulseaudio and pavucontrol make it easier to manage multiple sound outputs.