Had the same problem on Friday - had the green smoke for around 10 minutes. I really think they need to do something when these delays happens as it leaves a bad impression of the ride, and seems to happen a lot.
Other than that last train journey, it was the best ride I had on the ghost train. Staff on our train were proper going for it and made the evacuation seem really real. The train crash part was also really good due to the actors, chasing people and made everyone run.
Apart from a 15 minute break down just before we were going on the ride ran all day from 12 which was good, and was also the first time I've seen it with literally no queue.