Why would a sleeper ship be designed to only wake one person in case of emergency?
Starliners are huge colony ships. They carry enough equipment, building materials, embryos, colonists and nutrient rich rations to permanently establish a sizeable colony on a far-flung world. Although they're big, they aren't designed to act as generation ships. Instead any perishables (like people) are stored in 100% safe stasis modules (trust us, these things never cause psychosis or mutations) and running the ship day to day is entrusted to a helpful non-AI computer system (also 100% safe: guaranteed not to try murdering the protagonist with welding drones, and with no concerns about it trying to take over the universe)
However the ship designers know that there may be unforeseen emergencies. So every ship has a Troubleshooter (despite the name they rarely actually shoot the trouble). This individual is highly trained, augmented, decked out in Freeman class hazardous environment gear and given administrative privileges for every part of the ship.
They are also the only person ever woken by the computer en-route. No matter how bad things get, no matter how far outside of acceptable parameters things are, nobody but the single Troubleshooter wakes. There is no backup. No redundancy. This is, for some reason, intentional.
The question is why this would be so. Much like the drivers in this question: why would the people launching the colony ship not opt to include or wake multiple specialists in case of trouble?