Brakes controler

Thanks to all who responded to my question. I don't understand when I use the manual brake on the built in system the trailer brakes will stop the trailer, but when I apply the brake pedal the brakes don't work as well, even with the brakes set at a gain of 9. My previous diesel did not have the built in brake system, I had a Prodigy and it work great. I will do more research and testing of the brakes, but so far the explanation for the lack of brakes at low speed seems to fit with the issue that I am having.
Thanks,
Wayne