Tied notes aren't tied when exporting to mp3

Hi,

I'm trying to export mp3 of a choir score.
When exporting the whole score, it works as expected.

As I need to have a dedicated mp3 per voice (Soprano, Alto, Tenor & Bass), I tried the "Select parts to export = Alto", but the rendered mp3 gives Alto and Alto in the same mp3.
As found on MuseScore forum, I tried a second way:
I select all the notes (ctrl-a) and uncheck the "Play" property. Then I select one note from Alto > right-click > select > More + Same Staff + Same Voice.
Check the "Play" property.

When exporting it, only the expected voice is played. But all tied notes ... are not tied any more.
When playing the score with this setup, the notes are also untied.

Am I missing something ? Is it a bug ?
I attach a testTiedNotes.mscz as a demo.

Best regards,
Samuel