Hi there happy to help.
It sounds like you have your receiver in STEREO mode. This will cause the rear speaker issue you are having.
When listening to a source press RECIEVER on the remote and then press the AUTO/ALC/Direct button.
This will take you out of Stereo mode.
Let me know,
Ok, try this.....
Press RECIEVER, then press SBch. Make sure this setting is ON.