This is a strange one: I imported an instrument and audio only N4.3-32 project (took out all the plugins just in case) into N5.5.2-64-bit and one VST instrument track plays back but the Nuendo level metering for it appears broken. It feels like the metering is disconnected because I can change instruments or presets and the N5 meter remains blank; I can also insert a metering plugin and it works. The other tracks and VSTi are fine.
The simple fix was to instantiate the synth another time, move the MIDI over, and then delete the original track.
And I realize that moving from one version to the other isn’t recommended, but this is a young project and I needed the space 64-bit offers… Just thought someone should know.