Sounds like you are dealing with the same type of dealership I did when I first brought my truck in, after having it for 2 days. In addition to a very hard bump from 2-1, it would also slam into gear so hard it caused the truck to jump forward. This was with just 122 miles on it, and it did not do it when I drove it off with lot with 44 miles. They had the truck for 3 1/2 weeks and gave me the runaround every time I called for an update until I finally got Ram Cares involved. Finally, they ended up just putting a whole transmission in it since apparently they could never figure out the cause. It will occasionally bump from 2-1 still, but it is not very frequent and not bad enough I worry about it anymore. My Titan would make a pretty good clunk while slowing down every time the converter unlocked.