I’ve seen this before with other plugins over the years. Sometimes the developer fixes the issue when reported to them.
It’s easy to think this but over the years 99.9% of the plug-in fixes I’ve seen have to come from the plug-in developer which tells me that WaveLab wasn’t tested, or was under-tested, and corners were cut with VST3 coding.
Two obvious differences between WaveLab and Cubase/Nuendo is Clip Effects, and background rendering.
It seems that users of Sequoia, Pyramix, SoundBlade (RIP) and other more niche mastering DAWs suffer a similar around of 3rd party plug-in issues which again, goes back to the plug-in developers actually testing WaveLab and listing it as a supported host for their plug-ins. They likely don’t have the time, resources, or interest in testing more niche mastering DAWs.
Plug-in developers tend to list supported hosts for the plug-ins where as DAW manufacturers simply list which plug-in format their DAW can host (VST3, AAX, AU, etc.)
That said, there are a handful of plug-in developers that do write trustworthy plug-ins that perform correctly in WaveLab. FabFilter, DMG (good at responding to occasional issues), Goodhertz, Tokyo Dawn, Tone Projects, Plugin Alliance (most of them), Universal Audio (though they don’t list WaveLab as a supported host), Eiosis (fixed a no audio processing on rendering for me years ago), Make Believe/Metric Halo/Sontec (fixed a rendering quirk in WaveLab ASAP for me right after it came out), Schwabe Digital (spent a lot of extra $$$ in development making sure it worked in WaveLab since it’s a mastering plug-in), Sonnox, and probably some others.
NUGEN is one I wanted to use but just gave up due to providing them A LOT of info about the bugs I found and no action on their part. They are dead to me.