Audio not outputing to USB dac when playing video on RPi3

  • I'm on version 8.0.2 on RPi3.

    I've connected an USB Audio Class 2 dac to RPi3 and set it as audio output device (in KODI system settings / audio).

    When navigating KODI user interface or using KODI as an airplay audio receiver, I hear audio from the DAC just fine. However, when playing movies, the audio for some reason is always output to HDMI instead of the dac.

    How can I set the audio output device to be always the USB dac?