I’ve finally reproduced what you’re talking about Richard. And it happens with Wavelab 10 on Windows too. It doesn’t happen in Wavelab 9.5.
To reproduce make a 96k or 192k montage with 3 (or more) tracks (it’s easiest to make the montage in Wavelab 9.5 because then the montage will be readable in Wavelab 10 too). Add an audio file to each track and stagger the files so they don’t overlap vertically.
Put a plugin that doesn’t use the silent flag (thanks PG), like the built in Steinberg RestoreRig, as a track plugin on each track.
Solo track 1 (this will “mute” the other 2 tracks) and play the first audio file.
In Wavelab 10, the audio will probably be distorted or stuttering and the performance meter will probably be at full scale.
Now while it’s playing, toggle the mute buttons on the other 2 tracks. That should “fix” the distortion and performance meter. The Solo is “muting” the other 2 tracks but apparently not fully (as Richard said). This doesn’t happen in Wavelab 9.5, and seems like it should be fixed in Wavelab 10.
I actually did this with Wavelab Elements 9.5 and Wavelab Elements 10 but I would bet it’s the same in Wavelab Pro.
There’s still the subject of the VST3 silent flag I’m looking at because from what I can tell (somebody please correct me if I’m wrong) Cubase and Reaper don’t add extra programming to force all Track plugins to release processing during silence regardless of silent flag, any more than Wavelab does, so requesting Wavelab to do that seems like an unusual request. Cubase and Reaper just seem to rely on the plugin maker to enable the silent flag, or not, but I think there are a lot of third party VST3 plugins where it was not used (probably including at least some Plugin Alliance plugs). It would be worth testing the Plugin Alliance plugs one by one to see which of them does or doesn’t use the silent flag. It’s pretty easy to tell in a 192k or 96k montage. Then it could possibly be requested of the plugin maker to enable the flag. Whether they would or not is another matter. But if all the plugins used the flag you probably wouldn’t even have to use Solo as long as the files were staggered.
Or you could use your VST3 plugin chains in Blue Cat Patchwork VST3 and all the plugins would release whether they used the flag or not. Although Patchwork has some amount of overhead of it’s own.