I don't know your circumstances for buying out of state with a local dealer available but your falling victim to the didn't purchase it here issue with RV manufactures and dealers. I assume you saved more than the $260 not buying local so your still money ahead
Depending on the travel time and delivery method of the FW to the original dealer your problem could be as simple as the brakes need burnished in. If not, adjusting them is easy just google it or uTube it to find out how. A jack, an hour and couple beers, your done.
If its a problem with the trailer wiring and not the adjustment then go get'em, that is not a dealer issue but a manufacture issue. This is assumming your brake controller is working properly.