I'm not sure what's going on with the Goniometer, but it seems to be doing strange things with the output.
When I click on the MIX OUTPUT TO MONO button, it seems to increase the left level by 3dB, and the right level by 4.6dB, which shifts the stereo (mono) image to the right (by 1.6dB).
The 3dB shift is workable, but panning the Mono output towards the right channel seems wrong,
Is there something wrong with the mono mode on the Goniometer ?