I use Aalto a lot with my Manta controller, which can send pad pressure as polyphonic aftertouch. I just re-opened a patch I used a while ago (almost a year now) and now I'm hearing substantial zipper noise when I modulate the filter cutoff using poly aftertouch. I'm not sure if I just didn't notice it before or if something has changed.
1. start with the Aalto Default patch
2. set the shape to sawtooth to get some harmonics
3. route polyphonic aftertouch to filter cutoff
4. crank up the input scaler on filter cutoff
Particularly on higher notes, modulating pressure will sweep the cutoff, and the noise sounds pretty bad.
I'm not sure what the right general approach is here, given that for the waveguide frequency I actually make use of the discontinuities that come from mapping the low-resolution MIDI data (the jumps sound awesome), so I wouldn't want everything to be all smoothed out. In that case though I'm doing the control through MIDI mapping in my DAW, so at least for me it would be a good fix to just add some smoothing to the polyphonic aftertouch signal within the Aalto patchbay.