There are usually a dozen or more riders collecting time penalties at PBP, for a variety of reasons. Sometimes that bumps them over their maximum time allowance. A friend of mine got a 2 hour penalty in PBP99 when his family got lost and were driving on the riders' route not too far from the finish.
From
https://www.paris-brest-paris.org/index2.php?lang=en&cat=randonnee&page=reglementSCALE OF PENALTIES
Overtaking official vehicles at the start of the event 1 h
No lighting at night, or under conditions of poor visibility 1 h
Violation of the French traffic law - Use of cell phone while riding 1 h
Drafting with someone not taking part in the event 1 h
Environmental pollution 2 h
Absence of (or hidden) reflective vest at night 2 h
Refusal to obey controllers 2 h
Registered vehicle present on the official route although the driver pledged to follow the special itinerary. 2 h
Support given on the official route, or in the control towns, by a non-registered vehicle 5 h
Incorrect behavior of rider or support crew towards the controllers 5 h