Offizieller Kommentar
@Aditya > Thanks for the video - it helped clarify my hunch, which is that it's a misunderstanding of the control.
In this situation, the LEVEL/DEPTH knob is used as a WET/DRY mix control. You may notice that the difference between 12 o'clock and 5 o'clock is that at 12, the beat from the music is audible right at the start, but at 5, there is a 1 beat delay - because you are hearing ONLY the echo audio and not the source audio. If you adjusted the timing to 4 or 8 beats, this would be WAY more apparent.
The echo on the S9 works differently as there is the ability to adjust that parameter, whereas the 900NXS2 doesn't have a second parameter for the echo. If you want an infinite echo, I would recommend using the ROLL effect instead.