I was wondering why a piece I was working on had extra notes at the beginning of the MIDI file, and I traced it down to this strange bug.
It’s easily reproduced from a blank piano score: with a 4/4 time signature, place a whole note trill on the 94th measure or later, and export the MIDI with a non-silent playback template. Extra trill notes appear at the beginning of the MIDI file, and some trill notes are missing from its actual position.
Tempo does not appear to affect it, and this happens in any equivalent meter as long as the trill is placed on or after the absolute 374th quarter note of the piece.
incorrect_trill_midi.zip (410 KB)