manual positioning of chord symbols on staves other than top staff way too low on reload

Steps to reproduce:

1) load attached score
2) drag the first C chord anywhere - even just a small amount
3) save
4) reload

Expected result: chord is where it was dragged too
Actual result: chord is much lower than it should be (below staff, most likely)

Only seems to affect chords attached to staves other than the top staff of the system. Presumably, the starting point for the offset is being incorrectly calculated. This only affects chord symbols as far as I can tell. I am investigating further.

GIT commit: 3543170