The problem may be depend on AirDrop's bug and we can't find / fix it correctly.
If you see the following alert box on receiver's iPad / iPhone,
please download the dummy setlist on receiver's device and import it into Piascore once. It's easiest way to open this page on iPad / iPhone and tap the following link.
After importing, you can share setlist file via AirDrop.
(Please delete the setlist "Piascore_dummy_setlist" in your app).