yup both of those example should play audio through both output channels.
Check the presence, values and soldering of the associated components:
- the connectors:
- the output jack
- JP3 and the mating connector on the Bela cape
- components:
- R50, R51, R52, R53, R54, R55, R56
- C16, C17, C18
- Also check that there are not unexpected sorts on pins 5, 6, 7 of IC1.