Mainstage 3 Sending TWO Program Change MIDI Messages

I'm having a problem sending a Program Change MIDI Message from Mainstage 3 to my Roland TD-12 drum module.

I've created an External MIDI channel strip in my patch and assigned it to my USB MIDI controller on MIDI channel 10 (which is plugged into the Roland - channel 10 is the channel that the Roland is set to receive on). I've then set the patch change number in the channel strip to 20.

Problem is that, when I select the patch in Mainstage, the Roland always sets to Program 1, no matter what it was previously set to..

When I attach a MIDI monitor in place of the Roland, I can see that Mainstage is sending two PC messages: -

1: Program Change, MIDI channel 10; Program # 19

2: Program Change, MIDI channel 10; Program # 0

These 2 messages come in at almost exactly the same time, but they always come in in the order shown above - first a PC to program # 19, then an immediate PC to program # 0. The result is that the Roland always goes to program # 1.

I've looked around at other settings (in Mainstage Preferences, at the concert level and also the patch level) and, no matter what I try, I still get two PC messages.

Any help would gratefully received. Thanks, in advance.

Darren