I would get this fixed right away
before you get water entering and water damage. There is plywood behind the outer gelcoat on your side wall and back wall and it will absorb moisture and swell and you will start to get delamination as well.
I would cover those separations with tape right away in the mean time. Something like Clear Gorilla Tape so you can still show your warranty service advisor the problem thru the clear tape.
My 2015 Vista has full length aluminum corner moldings that fasten the rear wall to the side walls. In the attached photo you can see vinyl strips in the moldings and behind them are self tapping screws every few inches that screw into metal edge joists in the side wals and rear wall. They snap in the vinyl strips after they place all the screws. Either those corner moldings did not get installed at Forest City when they built your unit, or they changed the Vista design sometime after 2015 and now secure the back wall to the side wall in some new way.
I've attached a photo of what my 2015 looks like. The vortex generators are owner add-ons. The tan duct tape along the bottom of the side wall is an owner repair.
Also, the bumper should be vertically straight not cockeyed. You should have them address that , too.