I had a similar thing our last trip out. Going out, it was perfect, no sway and 60-65 no issues on the 100 mile trip. Coming home, I got out onto the road and knew something wasn't right almost immediately. I would get to 45-50 and it just didn't feel right. I ended up pulling off immediately into a truck stop. I adjusted my equalizer hitch one more notch on the bracket and let about 10psi out of my airbags.
It ended up working out perfect again.
Since it was our last trip out for the year, I have to get used to the setup and play with it a little more next year.
I'm sure you'll find it was a quick adjustment though.
2012 Keystone Sprinter
Still sticking around for the good people and advice.