Audio sounds through only the left channel

[Edit] Originally you could find here a recipe to fix a Dorico project file from the left-only issue, but as Dorico evolved over time, this recipe did not work anymore, so I deleted it. Instead, if you also ran into that problem, please send the affected project file to ‘u dot stoermer at steinberg dot de’ and I will fix it for you.
Please also note a related section from the Dorico FAQ:
" On macOS, AirPods and Bluetooth headsets easily bring Dorico’s audio engine into trouble due to the low spec built-in microphone. So here is the recommended way of dealing with them on Mac:

  • Stop Dorico
  • Make sure that the AirPods or Bluetooth headset is working with other apps, e.g. Apple Music.
  • Launch Applications/Utilities/Audio MIDI Setup
  • On the Audio Devices page create a new Aggregate Device
  • In that device let only the stereo outputs of the AirPods or Bluetooth headset participate, nothing else
  • Optionally, rename that device to your liking
  • Start Dorico and go to Edit > Device Setup
  • In the list of ASIO drivers your newly-created aggregate device shall turn up now. Select it, close the dialog, done.
  • Don’t get tempted to select the other AirPods or Bluetooth headset related entries in the ASIO driver list: you might end up with situations where only the left audio will play out and it’s difficult to recover from that."