The data in the session I put up indicates that moving the faders in the mixer is recorded with MUCH higher frequency.
That particular bad behaviour may me MacOS specific, since I'm on Windows 10 and have good data on my mouse-driven volume envelope recordings.
That session is here for anyone to inspect:
https://stash.reaper.fm/37319/MCU%20...automation.rpp
CSI is the exact same. Same data. So CSI is working just fine, but something is not working well enough right now in Reaper itself. That's what it looks like to me.