Google Play Games: loaded snapshots are always empty

I'm trying to save and load snapshots with Play Games library but I'm stuck: I send my byte array and, I suppose, it is correctly saved in cloud because if I start the Intent given by

Games.Snapshots.getSelectSnapshotIntent(...)

I can see the saved snapshot.

On game restart I want to load the snapshot in background. Here the problem arises: the returned byte array is always empty and the saved snapshot is deleted from the cloud when I try to load it.

How could I save/load snapshots in the right way?

Snippet of the saving background method:

Snapshots.OpenSnapshotResult result =
    Games.Snapshots.open(gameHelper.getApiClient(), "test_filename", true).await();

switch (result.getStatus().getStatusCode()) {
    case GamesStatusCodes.STATUS_OK:
    case GamesStatusCodes.STATUS_SNAPSHOT_CONFLICT:
        Snapshot snapshot = result.getSnapshot();
        snapshot.getSnapshotContents().writeBytes(data);
        SnapshotMetadataChange metadataChange = new SnapshotMetadataChange.Builder()
            .setDescription("Modified data at: " + Calendar.getInstance().getTime())
            .build();
        Games.Snapshots
            .commitAndClose(gameHelper.getApiClient(), snapshot, metadataChange)
            .await();
        return;
    default:
        throw new Exception();
}

Snippet of the loading background method:

Snapshots.OpenSnapshotResult result =
    Games.Snapshots.open(gameHelper.getApiClient(), "test_filename", true).await();

switch (result.getStatus().getStatusCode()) {
    case GamesStatusCodes.STATUS_OK:
    case GamesStatusCodes.STATUS_SNAPSHOT_CONFLICT:
        Snapshot snapshot = result.getSnapshot();
        byte[] data = snapshot.getSnapshotContents().readFully();
        Games.Snapshots.discardAndClose(gameHelper.getApiClient(), snapshot);
        return data;
    default:
        throw new Exception();
}

Note that I haven't any conflict or exception and that even with the SnapshotsCoordinator helper I didn't get it to work.

Play services version: 10.2.1