phnuff,
Happened "Loads" of times with "Various" airlines. A/c has a rather more than a "minor" prob. Can said a/c depart "safely"? if ANY doubt, a/c rtb pdq and a "reserve" [not necessarily] same co a/c does flight. Better 2-300 digruntled pax rather than xx hurt or worse.
we aim to please, it keeps the cleaners happy