to set the currently playing track in the playlist and it works unless i try to set the index to "0". Of course 1 sets the currently playing song to 2 in the list, 2 to 3, etc. So i would expect 0 to set the currently playing song to the first song.
Which build do you use?
I tried and it seems to work ok for me. Setting 0 sets first track in both situations - when no track was set before as playing and even when other track was playing. Tested by simple script, which just call app.player.setPlaylistPosAsync(0); on button click.
How exactly do you test it?