AI question - attack routes issue?

I've been trying to make an attack route for an AI player (single player scenario style), following the example set by "The Dwarven Forge" (Mission 23) and "The Well of Urd" (Mission 27). However, I can't make the AI follow the chain of cinematic blocks even remotely close. If they have LoS on the enemy base they'll just balls off in a random direction until they arrive there. This does not seem to happen in the campaign missions though, despite me using the same functions.