when we created the Undulator for the Orville, long time ago, we analyzed the same fx in the H3000 and built a structure with complex dynamic modulation (=your signal level controls the modulation rate) of different fx, delays+detuners+tremolo.
The interaction between these fx and the dynamic sensitivity provides a very organic way modulation reacts. Particularly, when the signal fades…you may hear that modulation rate is not following any constant wave pattern. Is this what you hear? Where exactly you hear what you report? Are you using a factory preset?