I had similar issues with my 2009 2500 Express van. It lived most of its life in the north where they salt the roads heavily during the winter. The pushing the brake pedal thing also applied to my van. It would straighten up and act right briefly.. I was getting all kinds of codes like lost communication to the BCM and just odd stuff. The van would also just stop running wherever it felt like at the moment but would typical restart and run after pushing the brake pedal, very hard at times. Long story short, it turned out to be a corroded and failing braided ground strap on the passenger side from the chassis to the transmission. I was under there looking at stuff and happened to grab that strap and it was just crumbling in my hands. I replaced it with a piece of ground wire used for grounding networking cabinets. If you do find that to be the issue I would recommend using stranded electrical wire with a jacket. Stranded will hold up better than a solid conductor wire in a moving, vibrating, pot hole hitting moving object. I would also be sure that it is substantial enough to carry the current that the original strap did. The strap was about an inch or so wide and about an eighth of an inch thick.