MPC sending MIDI on every Channel

I’m using my MPC Key 61 which is connected to a number of rack modules. So for example. I connect my MPC to my Roland J990 which is set to MIDI Channel 1 On my MPC MIDI track regardless of what channel (1 to 16) I select on the Track MIDI Output Channel the keyboard still triggers the J990 and plays whatever patch I have selected. If I change the MIDI channel on my J990 it still sounds regardless. I can only conclude that regardless of what channel I select MPC transmits on every channel! I am using MPC 3.6
Would be very grateful for any advice / help .
Thanks, Michael

is the J990 somehow inadvertently in Omni mode to receive MIDI In?

Thanks for your reply. I’ve managed to solve it. The problem was that for some reason when the rack synths were set to channel 1 they received MIDI on all 1 to 16 channels. I’ve got each separate rack now on 2, 3 and 4 and works fine with MPC track MIDI channel selection.
Michael