I see same problem with IK Multimedia (SampleTank 4 and Amplitube 4) plugins, so I use SWS snapshots when its critical that I may need to undo changes.
What I don't get is, why can SWS snapshots save and undo param changes for these IK Multimedia plugins but REAPER can't?
REAPER can record their automation, so why can't it save their params and undo them?