Fatal Error Code

The dishwasher started giving error codes yesterday and refused to work.
Investigated further this morning and it could be the heater relay but was more likely the pressure sensor.
When I got it out I found the bottom of the casing at the back was badly rusted and the most likely culprit was the salt tank/water softener.
All in all a good case for replacement.
When looking through options we came across an advert saying “Miele - Engineered for a 20 year life.”
So how come ours only lasted 16?