Same here:
After some hours, audio does not get routed to the plugged-in headphones, but to the speaker (not to big one, but to the one you press your ear on when using the phone as a phone).
Unplugging the headphone and replugging it again does not help, it just switches between the big speaker and the “ear” speaker.
What helps is starting a phone call: The “phone” app seems to fix audio routing.
Never had this issue with my Xperia X, on the 10 III it happens frequently.
Edit: Random audio drops on wired headphones - plays from top speaker instead seems to be the same bug.