Hi @navmatt, glad your first trip went well. The breather hose should only fill once the tank is full and will then act as an overflow, I can fill my tanks at a fairly fast rate. Make sure there is no kinks in the fill or breather lines, if all is good make sure there is no thread tape obstructing the inlet/outlet fitting on the side of tank or you may have a leak around one of the treads. It's just a process of elimination if you want to fix it, otherwise it's a job for Jayco.
Good luck, let us know what you find!
Cheers.
Good luck, let us know what you find!
Cheers.