Use of & for measure overlays causes layout and playback issues

[seisiuneer]

As reported by Seymour Shlien, if an ABC uses & to overlay notes in a measure, you get odd visual layout and playback issues.

Mazurka_X1.txt is one of Seymour's arrangements that demonstrates the issues.

Mazurka_X1_stripped.txt is a version of the original with all the & overlays stripped. It lays out and plays just fine.

Mazurka_X1_stripped.txt
mazurka_X1.txt

[seisiuneer]

Here's mazurka_X1.txt brought into EasyABC, exported as MusicXML and then transcoded from MusicXML to ABC by my tool, lays out and plays just fine with the overlays split to their own voices.

mazurka_X1_MusicXML.txt