I have been creating a diagnostic plugin that shows the detail of cursor elements.
I have found that non-chord, non-rest elements exist in the score.
For instance the opening measure of the second staff of the excellent Reunion is a minim rest. This is ticklen 960 at score tick 0. This is then followed by 5 elements at score tick 240, 360, 480, 600 and 720 which are neither chords nor rests. I think these are there to align with the rest and 5 notes of the first staff.
Pure curiosity - what are they and what should they be called?
(The plugin documentation for cursor.next says this moves to the next chord/rest!)