One speaker not sounding

I have a stereo setup, subwoofer and L R speakers, all Behringer.
I loaded Metz (and subsequently other organs) but left speaker did not sound. Checked configuration and all connections, no problems discovered. Used an alternative loading configuration to load Paramount 341, all worked satisfactorily all speakers sounding OK.
Used a 3rd Alt Config to load Metz and again, all speakers sounding correctly.
Puzzling question how can on Alt Config stop stereo when the audio engine is set to stereo?

Keith

Using my normal blissful ignorance I have solved the problem. I copied all the menu screens from the configurations that worked properly and compared them with the data from the configuration not allowing the left speaker to sound.
I discovered under Audio Devices and Channels at the bottom of the screen a section for mapping the Output Channels. My good set had 001 mapped to 001 etc whereas my bad setup had 001 to 003 through to 003 to 001.
Corrected this and all is normal.
I'm left with the puzzle as to how this came about and I'm not altogether clear what this mapping is doing. However it now works.
Fortunately!! we are in Covid lockdown here in Melbourne, Australia so I have the time to fill in!
Keith

The Audio Devices and Channels screen maps the Hauptwerk output channels to the device channels.

In this screen, if you hover over one of the channels, and then scroll, the selection will change. It is easy to do this unintentionally and unnoticed, so I'd say this is a treacherous feature because you can mess up all your audio routing and have no idea what is going on.