[JRTJH]

It's impossible to guess where a leak in an RV originates or where it might drip into the underbelly. To the point, any fitting, any pipe, any drain, any appliance that uses water, any wall, any molding, any rain gutter (the list goes on and on) might be the cause of a leak of pressurized, waste or rain water that eventually finds its way into the underbelly.

If the dealer says he found it, fixed it and it's not a problem, then unless you find water there again, you've more or less got to believe him.