Everything works fine until you try to remove the melodyne instance.
After removing, Cubase will close instantly due to a crash.
The only thing that seems to work to avoid crashing Cubase is to make an empty audio track, add 1 melodyne instance and disable the plugin. Leave this track and plugin in your project and don’t remove it!
Now you can add, use and remove the melodyne instance from any other track without crashing the system.
I don’t know why, but you must have at least 1 melodyne instance in your project before removing other instances.
Hope this also works out for you guys!