iOS10 issue: MIDIClientCreate is blocking when iPad is connected with WLAN stick to Yamaha Tyros 5

Hi all

Is see a strange behaviour with MIDI since the update to iOS 10:

When the iPad is connected to the WiFi network created by the "Yamaha UD-WL01" WiFi stick on a Yamaha Tyros 5 keyboard, MIDI cannot be initialized anymore.

The function MIDIClientCreate (on line 11 in code below) is blocking endless (when debugging in XCode) and the app is ended after some seconds when started on the device.

Here some lines of code (bases on Pete Goodliffes PGMidi):

- (id) init
{
    if ((self = [super init]))
    {
        sources      = [NSMutableArray new];
        destinations = [NSMutableArray new];
        midiNetworkConnections = [NSMutableArray new];
      
        virtualMidiOutEnabled = true;

        OSStatus s = MIDIClientCreate((CFStringRef)@"PGMidi MIDI Client", PGMIDINotifyProc, self, &client);
        NSLogError(s, @"Create MIDI client");

        s = MIDIOutputPortCreate(client, (CFStringRef)@"PGMidi Output Port", &outputPort);
        NSLogError(s, @"Create output MIDI port");

        s = MIDIInputPortCreate(client, (CFStringRef)@"PGMidi Input Port", PGMIDIReadProc, self, &inputPort);
        NSLogError(s, @"Create input MIDI port");
    }

    return self;
}

What can cause that the MIDIClientCreate method is blocking and never returns?

Best regards

Matthias