changes to volta properties don't propagate to/from parts

If you change the text and/or repeat list (e.g from "1." to "1.+2." and "1" to "1,2" respectively) of a volta, after having created the parts, in either a part or the score, these changes don't propagate to the other side.
Data loss and inconsistencies arise, hence critical.
It is debatable whether the volta text needs to propagate, but the repeats lists surely should.