On the topic of crazy MC2 bugs...I have posted this before (years ago) as it involved a PR back then, but it definitely deserves its place in this topic:
Replay drives a faster time than the real PR!
The splits screen indicated a 1'08"97, which is the time I really drove, after which I activate the replay that runs a time of 1'08"73. It had to do with the final LB, which was crappy sideways in my real run (explaining the relatively poor final lap chrono), and not that bad in the replay. I know replays usually go off synch with sideways LBs, the game just can't handle those. Also, if the desynch happened at ANY earlier part of the race, it would have definitely gotten stuck in a wall somewhere.