One potential way to minimize new trailer delivery problems is to use a PDI checklist.
There are many PDI (pre delivery inspection) checklists out there, but I used this one as a basis for refusing delivery of my toyhauler a couple of years ago.
http://changingears.com/rv-checklist-inspection.shtml
The best protection you have if buying a new vehicle of any type is to not sign any contracts or paperwork until you have fully inspected it. When I bought the TH the dealer was upset that I wanted the inspection and kept trying to get me into the office to sign paperwork.
As a result of some major defects I refused delivery and did not get the trailer until 2 weeks later. There were other issues later that would not have been found in the PDI which had to be dealt with as a warranty issue. But as long as the dealer retains ownership, you do not have to accept delivery if something is wrong. And you should not if there are any problems. I told them in advance I was bringing a PDI checklist, sent them a copy, and told them I would not sign anything until the inspection was done.
My wife was inside the dealership while this was going on and saw more than one couple led into the office for paperwork, then coming back in an hour later stating there was a problem with their "new" trailer. They were told the trailer would have to be scheduled for warranty repair. Bad dealer? Perhaps, but I don't believe they are alone in doing business this way.