GarageBand stopped playing notes above a certain tone that used to play just fine.

I have a midi track I've been using on a song for ages, recently notes just stopped playing and now I have tried and looked into this for some weeks and have some science to report.

These are notes that used to play, they are electric guitars and changing between electric guitars has no effect.

Changing to synths or acoustic guitars plays the track as expected.

copy and paste of the track, changing to new tracks or fussing with note attributes has no effect.

Tapping on the note does not play the sound, but pushing it down a few notes into the zone that does play, the same midi note plays just fine. Pushing working notes up above the line and they also stop to play.

If you bring up a musical keyboard, you can play this note exactly as expected.

I see no unusual settings on any element from volume to pan etc. etc. etc.

All notes in this range above a certain note no longer play, all notes below the line play fine. As if the instrument itself was refusing to recognize notes that played just a few weeks ago and I have never had this happen in the past.

This is clearly a bug introduced into Garage Band or some element reasonably recently as I'm often working on the song and would likely notice quickly that these notes are missing.

I figure this is likely a know flaw but I didn't see a bug report about it, so I thought I'd ask since lots of folks must be running into this same issue?