This is a reproducible ?bug? (at least was not there before v25).
I use earphones with the Quest 2, and always plug them out when putting the Quest aside, then after a few seconds, the Quest goes to sleep state. When putting the HMD back on (waking it up) without the earphones plugged in, the Quest does not switch the sound to the earphones again once you plug them in. Thank god there is a workaround: you need to plug the earphones in before the wake-up, then they work, and also, plugging them out and in works as desired then (until next sleep state).