Thanks for the effort. We got similar results for RTX6001 loopback test as follows.
(1) DTP using variables
DAC AutoRanging at -3dB via [Setting]>[DAC Device]>AutoRanging;
ADC AutoRanging at -3dB via the DTP;
(2) Your ADC manual ranging DTP
DAC AutoRanging at -3dB via [Setting]>[DAC Device]>AutoRanging;
ADC Manual Ranging at customized thresholds (generally lower than -3dB) via the DTP;
The above are RTX6001 loopback tests. A DUT generally has a substantial higher distortion than RTX6001 and therefore the ranging artefacts will likely be hidden in the actual tests with a DUT.