The setups :
I loaded all 64 instruments from GPO and JABB to KP2 (the one that came with Garritan's library CD's). This used up all 4 midi ports (16 channels each) of KP2. Then, I routed midi tracks from my sequencer to the KP2 via four MIDI-YOKE (version 1.75) junctions (my sequencer supports multiple midi-out ports). The song that I played with sequencer, however, contains only 10 tracks.
Then, I tried playing the song in two different ways :
1) All the 10 tracks are routed to 10 different channels of the "same" midi-out port. This way, 10 Garritan's instruments played perfectly.
2) The 10 tracks are routed to 10 different channels that are distributed across the 4 midi-out ports (e.g. 3 channels each for port 1 and 2, 2 channels each for port 3 and 4). This way caused the problem. There are frequent "stuck notes" (midi message missed or lost) all along.
Well, in practice, option 2 is necessary for me whenever I need to use more than 16 instruments simultaneously. Any suggestion on how I may handle this problem ?