I'm running Zebra 2.3.1 in WinXP, Ableton Live 7.14. I'm not sure if this is a bug in Zebra, Live, or otherwise.
I'm holding a key down as I alternate between two of Menno's patches: "Hi-NRG" and "Jungle Fever". The issue is most pronounced when I switch to Jungle Fever -- I get an ungodly (well, to me; I suppose some will like it) noise that doesn't particularly resemble the actual patch. I think either Zebra or Live is struggling with what to do with a stream of midi data going into Zebra while there's a patch change.
![Confused :?](./images/smilies/icon_confused.gif)
EDIT: FWIW, same issue in Reaper 2.54.