I just recently went from a 2017 Ram Rebel 5.7L gasser to a 2019 Ram 2500 6.4L gasser and I also have the first push softness and if I release and re-apply I have a firmer and higher activating brake feel. My old Rebel brakes felt firm and solid on every push, never had a need to do the release and re-apply game that this one has. Honestly, my 2004 Grand Prix that I just did new calipers/rotors/pads on last fall has a much faster responding (higher in the stroke) and firmer feel than this 3/4 ton truck.
It has annoyed me, but I have not acted on it as I assumed it was something in the design of a larger and heavier brake system. But seeing this thread makes me wonder if the brakes on the 2500HD I bought are similarly effected by a component that is not performing as it should?
I have 1,400 miles on mine so far, but I have not towed yet. I do not expect to have my Coachmen camper out for at least a few months yet, and I'm not hauling the tractor for brush hogging in the winter.... so I have time to address this if we discover it can actually be effected with the replacing of some parts.
I will be waiting to see if anyone has success in getting rid of that double pump issue.