Warning: Extreme Geekery Ahead!
I love Star Wars, but I increasingly dislike most everything outside of the original trilogy. There's simply too much out there, to the point that people are forgetting why some things were introduced in the first place. Case in point: back-up hyperdrives.
The back-up hyperdrive was invented to cover a plot hole in The Empire Strikes Back. When the Millennium Falcon's hyperdrive goes out in the Hoth system, they somehow are still able to make their way to the Bespin system. How did the Falcon travel from there if its hyperdrive wasn't working?
This was solved early on in the West End RPG by saying that all ships larger than a starfighter have a back-up hyperdrive. Much slower than the main drive, and with less endurance, you'd still want to get the main fixed as soon as possible. It was basically the equivalent of a "donut" spare on a car. Thus, a plot hole in the movies is fixed to nearly everyone's satisfaction.
Fast forward a couple of decades and back-up hyperdrives are now an accepted part of Star Wars lore, but the people behind the new Haynes Millenium Falcon Owner's Workshop Manual seem to be clueless as to why it was introduced in the first place. Instead, they see it as introducing a plot hole, because why would the Falcon have needed repairs if they had a back-up? Thus, they say that due to the extensive modifications made to the ship, the primary and back-up hyperdrives share a motivator, so when the motivator goes out on the Falcon it takes out both!
Congratulations, you just undid the whole reason the back-up was introduced in the first place, and we must once again wonder how the Falcon got from Hoth to Bespin without Han and Leia having died of old age during the journey!