All disc brake actuators have some delay while they build pressure. Hydrastar is supposed to be one of the quickest. But an additional problem is that they all have a voltage level below which they do nothing. Google for my thread "Disappointed in Disc Brakes." https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29930221.cfm
I found my main problem to be turn on voltage with light braking. Because my 2012 F-350 did not have the "Low/Med/High" setting I had to resort to a Prodigy P3 to get the actuator to start working on light braking. The "Low/Med/High" setting, as I understand it, determines how aggressive the voltage back to the trailer is on light braking. I would try High to see how it affets things. After the brakes are set in, I would be surprised if a 9 setting didn't lock up the brakes.