2018 2500 159-HR
My house negative is isolated from the chassis, so everything round-trips. There are varying opinions here on whether the chassis ground should be used for the house DC negative and my preference is not to.Did you run your DC-DC negative to the chassis or back to the main battery?
The starter battery clamps to the chassis under the floormat in between the seats, so I ran 4 AWG over to an 'intermediate' chassis ground point I created from the D-loop behind the driver seat. I then run all my chassis (and component body) grounds from there, as well as bond it to shore ground when plugged in. So if by "DC-DC negative" you mean the channel for the starter battery then the answer is yes, but my shore power channel is not grounded to the chassis. (Again, there are many related debates on this and about every boat or RV or van forum).