I have the same problem. Seems to be worse when switching between two presets that have different output levels set.
For instance, I have one preset with a big hall reverb with a high mix setting and therefore I've increased the output level (3db or so) to compensate for the perceived drop in dry signal. I have another preset with a small spring reverb, a low mix and therefor a unity output level. Switching between these two presets, whether via MIDI or footswitches, leads to a couple seconds of wildly varying output volume. It's a real bummer because you simply cannot smoothly transition between presets. I really hope it gets fixed. You end up having to spend a bunch of time managing settings and carefully considering transitions to avoid the wobbly preset changes that I haven't experienced with other units.
