As others have noted, this is fixable. When it comes to "quality control", new RV's are going to fall closer to an inexpensive new house than a new car. There are a lot of systems that have to fit together in a small package. Sometimes the things don't get put together quite the way they are supposed to. Once you find something, you have to get it fixed. You are fortunate that there is a warranty that will take care of this without it being on your dime.
Now that it will be going back to the dealer, go look for other things that need repair so you can get them taken care of at the same time. The tank issue doesn't sound so bad that it would make the unit unusable. Take a camping trip to a place close to home. Set it up the way you plan to. Use all of the systems over and over. Use the heat even though it is summer (at least run it long enough to really give the heater a workout). Anything you find add it to your list and get it all fixed at once.
The good news is that once you get through this, your camper will be better than new and you will know more about it.
