On the grapevine, heard from a friend who has a brother who works there.
They heard it was human error. The ride was fixed for a sensor error early in the morning and an empty car was sent round prior to a car with passenegers ( who were the ones in the accident ).
The previous empty car was not weighted correctly and so when released at the last braking stop it did not have enough momentum to carry it up the last "hill" into the station braking point and slipped back down the hill to end up in the position we saw the crash, as when the car people people was released there should have been an empty track.
Obviously if this is the case no auto sensor system was in place to detect such a problem, because if there was, it would have overridden the car release instruction and they would not have crashed into the ghost car.
Anyway as i say this is just hearsay and may well be utter rubbish but sort of makes sense.
In my mind surely only emply cars can be sent round in some sort of engineering mode, so how a full car was sent right afterwards without the emply car being back in the station doesnt make sense.