THE_FPV

Could it be the hill start assist holding your brakes? You said it's worse on an incline. I notice my 2021 definitely does it as well, I was thinking either the hill start assist is engaging without it showing on the dash or possibly a slip yolk issue (from recent experience) I'm new here and just spitballing.

Probably just your park lockout switch that requires you to have your foot on the brake to shift from park.

I had this happen to me as well, best I could tell was some kind of short or signal interference with the trailer brake controller. Pulled everything out, cleaned, dielectric greased some connections and wrapped up some junctions on the harness and haven't had any issues since. You would have pretty serious flat spots on your tires doing 62 miles an hour, if not, likely the trailer locking up and not the truck. Well, my experience at least.