Traktor is often unresponsive to my MIDI controller?

Whenever I boot up Traktor, there's a ~50% chance that it won't actually respond to my MIDI controller!

When I use the controller, Traktor's "CTRL" indicator lights up, so I know it is receiving messages. But often it will simply not respond — the corresponding faders etc within Traktor don't do anything.

To fix this, I usually go through everybody's favorite debugging process — try rebooting Traktor, trying unplugging/replugging the controller, try restarting the computer, try all of those in different orders, until it starts working.

This has become a real problem as it makes it very time consuming to get ready to play a live show!

Does anyone have similar problems, and/or advice for fixing this?

I use an Allen & Heath Xone K2.

 

I have figured out part of the problem — my mapping expect all of my controller's signals to be on Channel 15. However, sometimes (unpredictably) my controller sends its MIDI to Channel 16 instead. Now I'm trying to figure out why this is and what to do about it.