Odd to me that you of all people in this thread would ask this.
Just from your own recent posts in this thread, you're pretty knowledgeable on hardware, and appear to have a recent Sony 790 and OPPO 93.
FWIW I agree with others in this thread who've said something like: "the Panasonic 500 manual sucks BIGTIME!"
For the moment I'm actually enjoying USB HDD redbook stereo (in the background) on this player. Give me a few hours and I'll post my main settings, audio and otherwise.
Likely something so obvious that it'll bite you when you finally find it!