The problem goes away for me only if I copy the MIDI notes from inside the MIDI clip (it doesn’t work if I copy the MIDI clip itself) and paste it into a new MIDI clip. So it’s clear that the problem is in the MIDI clip and not in the MIDI clip’s data (the MIDI notes contained witin it), the track or the VST instrument.
This happened to me on literally the 1st instrument track of the 1st project I created since I purchased and installed Nuendo 8. Not a great 1st impression of a piece of software that costs $2.000.