The error is expected if your Logging Level is set to “LOG” in the FMOD Unity Integration settings and you unplug headphones. What isn’t expected is a deadlock/hang of any duration- did you get a hang as well or just the error?
Ah yes my mistake, it is an error and not a log message.
We could possibly downgrade it to a warning to avoid confusion, I will suggest that to the Dev team.
In any case, if you are removing headphones and everything is otherwise working fine then this error is safe to ignore.