Delay before in-place rotation

Dear ROSers, so I've successfully setup my navigation stack, going from point A to B etc. However, even with a rather flexible tolerance of x,y,theta I see a delay before the in-place rotation kicks in. The velocity parameters seem to be correctly configured since the trajectory is executed correctly and the rotation as well. The question: Which parameter ought I tweak in order to start the in-place rotation directly as soon as the goal location (and their tolerance) is reached? thanks a bunch, Karsten