I’m getting this type of problems with Wave V9 plugins on a Mac (Those on PC seem Not to have the issue)
In testing the only way so far I have been able to use the plugin to avoid the crash is to open the plugin menu (small arrow top right of plugin window) and select the generic editor which effectively bypasses the Plugins GUI. Not really ideal but stopped the crash and does allow you to keep working on the audio. Looks like an issue in GUI processing on some plugins on a Mac.
This occurs in both High Sierra and Mojave versions of the OS. Current Steinberg suggestion update the plugins. However that brings other potential problems in respect of Wave plugins as versions 9 and 10 cannot co exist.
Here’s hoping Steinberg can find a fix as I hate these “us or them” software compatibility issues between manufacturers.