I understand that your actuator isn't coming on for a few seconds ... I was just describing mine as coming on instantly. If indeed your actuator on your fiver is a HydraStar and your truck is a Ford or Chevy between the years of 2007 - 2017 with the integrated brake controller ... you
may have to install an adapter to make it work right.
There are several sites discussing your issue in one fashion or another ... try this one for starters. Read all the way down and see if it applies to you.
https://www.etrailer.com/p-HBA-CAM.html
What others have said could apply in your case as well ... I'm just offering this up for you to consider.