We all could look around and choose some poor guys 1st trip problems with a new or used unit and start a thread that justifies why we should/shouldn't buy a new or used unit. We see threads like this every day when looking through the many rv websites. This won't change anyone mind.
I've bought three new truck campers and three used 5th wheel trailers.....and they all were back at the dealer at one time or the other. BUT always after I did my full pre ops at home.
The moral of the OP story should be "why we should do a pre ops at home"...with a new or used unit.