There is likely a wire issue so just carefully inspect the wire on the speaker that is causing issues. Maybe it has an odd strand at the AVR or at the speaker. Maybe a banana issue, recheck it all.
If using the Sony BT remote just keep hitting "audio" on the remote and it will scroll through your options.
I am sorry, on the game remote you hit "select" to pull up the display. Hit "triangle" to pull up option menu, go into "Audio" and select the format you would like to use.