[LAD] MidiSport vs. UA25

Greetings, I've been experimenting with MIDI control from one machine to another. I checked the timing of a single note played simultanesouly by instances of QSynth on both machines and was surprised to hear a very noticeable flamming. I then replaced the MidiSport 2x2 with my Edirol UA25 and the flamming disappeared. Both are USB interfaces, btw. MIDI routing between the machines is handled by a Yamaha MJC8 and has never been problematic with that box. So, my question(s): Is the MidiSport just poorly designed and is there a further condition or module option that can correct the timing delay from that unit ? Best, dp