The armoured vehicle was stationary for between 38 and 43 seconds after the collision, the inquest heard, as soldiers shouted "wait" and horns sounded.
A stop call was sent at 10:25, which halted the exercise.
A built-in alarm system, which would have sounded a noise and shown a light to indicate the rear doors were open, did not work as a wire was broken, the inquest was told.
Col Watson said: "The built-in alarm would have alarmed because the rear doors were open, and had that gone off the driver would have almost certainly stopped."
Alarms had been installed on Warriors after two fatal incidents in the 1990s.
Col Watson said several faults with the armoured vehicles were known about, but he told the inquest that these had not meant the vehicle should have been taken out of service.
The inquest also heard the FV-511model involved in the incident was not ordinarily used for disembarking troops and close combat.
"The student commander had done the majority of his training on the FV-510, which is the platoon variant of the vehicle," Col Watson said.
"In general, the crew and service personnel within 5 Rifles were not that familiar with the FV-511 and its differences with the FV-510."