I'm glad my experiments led you to conducting more investigation, even though it turns out I was re-creating only what I heard on the track, and not what you actually played.
So it's a matter of anomalous overtones after all! I've run into that now and then with tuned percussion, and thought maybe that's what was going on here - but I couldn't re-create it. And I still can't, even after your new post. What we're hearing on the recording might be the result of the Celesta's sound mingling with the other instruments in the track? I'm not sure.
Just now I played your notes in unison octaves, but the ghost notes, F# and G# weren't there, so interaction with the rest of the track seems like it could be the other ingredient causing those notes to be heard.
I did hear, however, that the lowest C isn't in tune with the higher C - the two don't sound very pretty together. There are other notes which aren't too pretty on their own, like the A in the 2nd octave up is very "thunky" and of questionable pitch.
I downloaded your screen capture - it apparently was accidentally truncated, because the only section in the file is where you click on the Cs and the G on ARIA's keyboard. The other sections you mention in your post aren't there - playing the passage as intended, or the slowed down track-
But it really doesn't matter that the .mov file isn't complete - Looks like you've figured out the issue. If you take the bottom notes out, and maybe layer in a Glock, you'll probably be ok.
I want to point out that the F natural and G natural in my staff screen capture, heard in my last clip, is a nice alternative to the C-G-C you were actually playing. That could be one of those "happy accidents" where something musically is accidentally discovered. Maybe you want to try those notes instead of your original phrase to see if you like them!