audio switching from HDMI to internal speaker

  • Dell Optiplex i6500

    LibreELEC-Generic.x86_64-12.0-nightly-20231122-8c6dced.img

    Is there any known reason why the Dell should suddenly and for no apparent reason start playing audio through its internal speaker rather than through HDMI to the TV?

    I eventually "rectified" the problem by restoring from backup (about 2 weeks old) but in the process have lost TVHeadend timers and date watched info on a number of videos