Hi @bazza and thanks for your question. First answer is that I don't know, and it's obvious from your question that you're testing correctly. That said, two things: 1) simplify your tests to make sure 2) see if there's any upgrade to the firmware on the IO Dock and 3) try it with other CoreMIDI software (e.g., MIDI Monitor, which is free). Also 4) check the Log in MIDI Designer to triple check. Unfortunately, I don't have an IO Dock with me to test right now. PLEASE come back and tell me how it goes.
Thanks!
Dan