You're right! Oh, please forgive me, how could I be so foolish?
Of course it's system-specific, and, yes, of course it's the fault of the 3rd party VSTs! Why, when everything was working fine in previous versions of Cubase, it was all just a fluke! We were collectively imagining it, even!
Thank you for your endless wisdom. My, I don't know where any of us would be without it.