When I read this post I knew the answer was going to be the plugin being used, not WaveLab. You should contact Focusrite. I highly doubt they have tested their plugins in WaveLab specifically.
Too many plugin developers only test Cubase and then assume the rest of the Steinberg apps will be OK if Cubase is OK which is clearly not true, and in my opinion this is why we see so many 3rd party plugin issues within WaveLab.
It would be very smart for Steinberg to do better outreach to plugin developers to see if they’re testing WaveLab specifically, have NFR licenses for WaveLab, and give them some additional info on how to avoid issues in WaveLab that we so commonly see.
Clearly, there are some challenges and common bug/errors that come up year after year with new or not perfectly coded plugins that I think could be easily avoided and save many headaches with a little effort.
When I decide to introduce a new plugin to my workflow, I put it through some extensive rendering tests before using it on a project. It’s a 50/50 chance that it passes my test or not and if it doesn’t pass the test, it’s no surprise. I then have to decide if it’s worth my time to report the issue to the plugin developer and get it working or just ignore it and not use it.