I found a annoying bug in Massive X.
When I try to automate the Unison On/Off parameter in Ableton Live, I correctly configure the Unison state on the timeline. However, as soon as I record the automation, Massive X automatically records the Voicing (number of voices) parameter instead, even though I never intended to automate it.
The problem is even worse: when I enable Unison, Massive X changes the Voicing parameter by itself and overwrites my automation lane. As a result, the automation no longer controls only the Unison On/Off state but also the number of voices, which is modified automatically.
It seems that the Unison and Voicing parameters are internally linked. As a result, Massive X automates the wrong parameter and modifies existing automation data without any user intervention.