I've noticed a small bug when running westhill reverse. You have to do it in practice mode (only tested in single player, should work in multiplayer aswell for the first car) so it starts timing when you pass the start timing line. The problem is that you start too far forward. This makes you not pass the starting line on the first lap giving you one lap less.

How to fix: Either move the cars backwards or the line forwards. If you move the line forwards you have to make sure not to create the same problem when running non reverse.