What do you mean by "slightly dis-engage than stops"? Does the car momentarily reduce how hard it is slowing down? Does the brake pedal drop a little?
If you have anti-lock brakes they may be falsely engaging. That can be due to knocking some rust or scale off the rotor and it sticks to the magnet on a wheel speed sensor. At low speeds the signals developed get weaker, and that debris can make them so weak that they drop out and the computer thinks that wheel stopped rotating. The anti-lock function turns off below about three miles per hour. If it was reducing brake pressure to one wheel, that brake will start working again below that speed.
A rubber flex hose that is becoming constricted can make it hard for the brake fluid to get through it. That often shows up as the brake pedal is a little higher and firmer than normal, and it drops a barely noticeable amount as the car comes to a stop. As it gets worse that brake will not release properly, it will get hot, and it will be harder to get the car to accelerate.