I have an NCE powercab and am trying to consist an Athearn 911 first responders diesel with Tsunami 2 to a Bachmann GP38-2 with Soundvalue decoder. I was able to consist them but when I place them apart to test their operation I notice that the 911 moves out first at a lower speed step before the GP38 starts to move. They get further separated as they move. When hooked together it looks like the 911 is dragging the Gp38. Any thoughts?