After any race, AIs can't go to the pits, especially when a race/qualify ends. They go to the pitlane, but most of them pass ahed the pits, whitout entering and stopping the cars. It makes a enormous confusion at the end of the pitlane, with cars flying, crashing, etc. I would see those fixes in a newest patch...
[EDITED]
I know that it always happens when there are more than 12 cars in the race (a S2 friend told me today). It happens when there are 12 cars in the race too.