Could it be related to that thing whereby some AI cars fail to start under their own steam from the pits and basically they only get going if you manage to bump 'em from behind to move'em a bit? Maybe too low start rpm or something, I'm not sure of the root cause for that issue either but they may be related. And yes, it's not a unique issue, I think I had something like that happen to me too once... without talking of the fact that the AI driver usually forgets to pit and runs out of fuel on track