Lemons in the RV industry (unlike the auto industry) are common due to antiquated building methods. The product is rushed through a quick inspection and then out the door.
What one may experience with their trailer doesn't mean you will have the same problem with a similar model. I recently had a 2011 cougar 30ft, (our second Cougar) and had few problems as mentioned above. Our only reason for trading was to get a larger 5th wheel. We ended up buying a Sprinter which is also made by Keystone, because we have had good luck with their products in the past. As with all RV's, consistent inspection by the owner is important to stay on top of any issues that may come about, like caulking and seals, running gear, etc.