SimpleMIDIFile: Wrong midi output on Mac

Hi everybody,
trying to control an external midi device playing a midifile with SimpleMIDIFile in Supercollider on a macbook (OS 10.14.6) the signal is not routed to the selected midi out but instead the internal Apple DLS Music Device is responding to the midi messages:

x =“a Direction”);;

If I send noteOn everything is working without any problems:

m =;

Anybody knows what could be the problem? Do I have to define the midi channel somewhere else?

Thanks in advance fo any helps!