As title suggest it is about full repair your car at rally events after stage 2, 4 or 6.
So How to Do It?
It is really simple, of course its a bug or glitch, but I don’t expect Milestone to fix it.
So for example after 2nd stage your repair time is over and you have some still parts to repair.
So exit the event. Than return to event. Parts from previous save will be repaired and you can repair rest of the parts (and over and over until your car is fully repair)!