Legacy

Was there a specific reason given for why this planet fell short?

None that you've heard. Crewmen like you aren't involved in meetings about Candidate Worlds. Those are between the heads of the Stargazer Caste, the Lord Commander, and the rest of the Royal Family. And the details aren't really made public either.

That's politics, you guess.

If the ship had paused for proper repair at the previous worlds deemed 'unworthy' of being our new homeworld, this wouldn't be as big of a problem.
...
So whether the 'Lord Commander' likes it or not, the ship has to at least take a pitstop here for a full repair/damage report.

Your job as a Maintainer would probably be a lot easier, if the Worldship spent more time in a star system before jumping away. If nothing else, the way the jump drive takes longer to charge these days gives the Collectors some time to gather raw materials from nearby moons and planets. With that, it's easy enough to manufacture replacements for damaged bits of hull, spent fuel and air, and patching up the infrastructure.

Even so, the ship doesn't have the facilities to manufacture all parts it needs. That, or the facilities that could build 'em must've broke down over the years. Even if you stopped here for repairs... there's stuff that's just beyond your abilities to replace anymore.

And, far as you understand it, landing the Worldship on a planet is pretty much a one-time thing. It's meant to become the heart of the first settlement. It... wasn't really built to take off again after making landfall.