ES2 envelope attacks "shaking"

Logic Pro 10.4.8

MacOS 10.14.6 (Mojave)

I have three tracks all using the MicroPulse preset. At random times (I've not yet found a correlation for when it changes), the tight sound changes to more of a long-attack sawtooth.

I can sometimes fix by selecting a different preset, then reselecting this preset on the main track menu. Sometimes that doesnt work but I can "copy channel settings" from one of the other tracks using this preset and then "paste channel settings" - but sometimes even that doesnt work.

In this video, the transport is STOPPED - no music is playing. https://www.youtube.com/watch?v=vj7cOxapOcI

Note how the ATTACK settings for ENV2 and ENV3 for the instrument on the left are shaking and are much higher values than the "zero" attack of the envelopes on the right (the "correct" sound of the preset).. I presume this is the problem. What is causing them to shake?

This seems similar to a problem I reported back in November when an ES24 instrument (Studio Brass) randomly went wonky and sounded "smeared". We never explained that one...