I agree, too low of volume of production, too many slapped together items on even the more well built coaches, not to mention design mistakes, etc. Take my own coach as an example, even though I bought it when it was 14 years old, there are several things I have found over the years that fell into the category of build / production mistakes, or egineering mistakes on the part of the RV manufacturer, even though my coach was a high end small class A, which they stopped making due to pricing themselves out of the market. When my coach was built it's MSRP was 119,000, at about the same time a similar length entry level Fleetwood Flair built on the same chassis had an MSRP of around $60,000, the difference is full body paint vs vinyl graphics, real hardwood cabinet work held together with screws vs particle board held together with staples, Aluminum roof vs EPDM rubber roof, Aluminum side walls vs FIberglass, Solid surface counters vs laminate, ...
Yet even with these better materials and somewhat better build quality, Here are a few of the factory mistakes I have found:
Alternator sense lead connected to the wrong side of the diode type battery isolator causing chronic battery charging problems
A jumper wire under the dash connected that should have been disconnected in this application which caused the rear yellow turn signal lights to light up with the rear brake lights (I spent a couple of years off and on tracing that one down).
My coach included a CB radio from the factory, the problem is they wired it to a standard ground plane style antenna on the fiberglass front cap, which only works right if mounted to a metal roof (depends on the radio waves reflecting off the roof to work).
The reversible Fantastic fan in the kitchen is wired backwards so that the air blows out with the switch is in the In position and vice versa. (this may not be a factory mistake)
Who knows what else previous owners may have caught and repaired.
This does not include where they cheapped out in places like using common crimp on wire splices to run power to the side marker lights, instead of using the weatherproof wire connector supplied by the chassis manufacturer even though it was right there, likely to save the price of the mating weatherproof plug.