Note overlap correction not working - fix?

Hello All,

I've been doing some MIDI file analysis stuff, and I need proper monophonic tracks. I had been using Logic's overlap correction to make sure overlapped notes are just "legato", not actually overlapping. I thought it was working okay, but it turns out that it doesn't actually do "what's on the box", so to speak. If I have a quick pair of grace-notes - like a mordent - the notes are detected as overlapped... cool. I choose to "shorten", and everything *looks* okay, but if I run it again, it still finds the same mordent to fix. And when I run my analysis (different software), it does find an overlap at the location of the mordent... so, it wasn't fixed.
I should note that these files are exported from Sibelius at a resolution of 480. Is there something I'm not noticing here? A setting somewhere? Maybe I need a higher resolution export from Sibelius? Why would Logic spot the problem, then supposedly fix it (it even looks fixed in the UI), but not actually fix it? If I run overlap correction again on the same track, it sees the overlap again, just as though it was never "fixed." Strange and annoying.

J.