Win 10, Fin 2012c
I occasionally find notes de-tuning on established pieces which normally have little to no problem. I've watched the Mod wheel on the Aria Player, and it doesn't seem to be involved.
I'm in a public area, so I have to consider that it might be electronic interference... someone's cute idea of a "jam" session?
However, as soon as I use the MIDI tool, and highlight a section, the problem disappears. It's good for at least one run-through, then it de-tunes again.