My rationale for suggesting contacting a lawyer immediately..Brand new, hasn't even taken delivery and it is leaking. That mean mould and rot. It didn't 'just start' leaking, either, I bet. Take possession and the problem then becomes the new owners.
But then, I am not lawyer, so anything I say is simply as a response to the situation. I have read enough stories on here of people that have spent years trying to get restitution and redress for their leaking RV's...usually without success, too.
I do wish you luck in your pursuit.
Gary Haupt