Imported midi parts corrupted?

So I imported an older project into Cubase 10 and everything is more or less there, except for one serious glitch. I have a midi instrument track with some recorded midi parts that won’t play. That is, I can click on individual notes and hear them, I can play the instrument itself live via midi, I can record new midi parts and hear them on playback BUT, no matter what I try, I cannot get it to play those previously recorded midi parts. I tried opening a new instance of the instrument and copying over the midi parts…nothing. I opened a different midi instrument and copied/moved said midi parts, same result. So, it is these specific parts and only these parts that have somehow become corrupted (there was a different midi instrument in the arrangement that isn’t affected).

I am looking for a solution, or a clever way to copy these notes into a new part so I can recover the music I recorded. Any ideas much appreciated!

I only experienced something similar with an instrument track midi part once, rendered in place with wrong settings, muting the midi forever. I never got that midi part back to life again.

Yeah, i’m getting the feeling this is one of those weird one-offs I’m not going to be able to fix…