An RV has all the potential issues of a house and a vehicle, so it's no surprise that even well-constructed units commonly suffer mechanical failure. RV manufacturers don't have the ability to build every item themselves, so they purchase many of the systems and appliances from third party companies, which causes quality control problems in even top-of-the-line models.
Approximately 30% of RVs will break down within two years of use. Almost 80% will need repairs by their fifth year of operation, and almost all will break down within ten years.