Sounds like the problems before Challenger's last flight
If anyone is wondering why they're being so cautious; it's because the Orbiter is incredbly fragile.
The day before Challenger made its final launch in January 1986, NASA had a problem with the orbiter's hatch. When the door closed, a couple of tiny pins should drop into place completing an electrical circuit which confirms the hatch is in place. That day, the pins didn't fall into place. Pressure tests and Mark One eyeball said the hatch was sealed and pressurised, but NASA didn't want to launch without absolute confirmation - they didn't want another Soyuz 11.
So a team was called to the Pad to replace the microswitches, they used a special aluminium tool to hold the hatch in place because they couldn't risk touching the orbiter's protective heatshield. After replacing the microswitches, they tried to remove the tool and found one of the bolts had become jammed. They couldn't use force without damaging the ship, so the only option was to cut the tool away. After a long discussion about potential damage to the orbiter, the risk from stray hydrogen boiling off the ET, they get a drill sent to the pad - the battery is flat from being left in the cold. A replacement was sent and the fix is finally made - but by then winds around the Cape exceeded the threshold for a safe return in the event of a launch failure.
The launch was scrubbed until the next day. The media had a field day that the Shuttle was a dog and made jokes about the staff who'd tried to get it to fly. Meanwhile, that night in Florida was the coldest on record.
So, the failure of one bolt probably lead directly to the explosion that destroyed Challenger.
Which explains why NASA are taking no risks with this one.