"Firstly, the rear wing support section was missing four bolts compared to the homologated version of the car, which Ferrari acknowledged was not compliant with the rules. … "Ferrari argued that “the excessive deflection was linked to the missing bolts” and insisted there had been “no performance gain”, but stewards noted the #50 Ferrari achieved its highest top speed on lap 380 out of 387 – implying there was a performance gain thanks to reduced drag.

"A Ferrari mechanic reportedly noticed the absence of a bolt at 3:23pm, less than an hour before the end of the race, but the AF Corse-run squad did not take corrective action.

I’ve also read that all cars were checked for this (don’t have a source for this though), and also considering the nature of this failure, neither the 51 nor the 83 should be affected.