For safety reasons, the master decided he was not prepared to sail again until the fault had been identified.
An investigation revealed vibrations had caused an instantaneous fault in the alarm system, possibly due to a loose connection. The fault lasted for only "milliseconds" before normal signals were restored, KiwiRail said.
No repairs were necessary and only testing needed to be carried out. A permanent modification to reduce the risk from vibration was being discussed with the manufacturer, KiwiRail said.
The Aratere has now been cleared to sail as scheduled at 10.45pm today.
Affected passengers were transferred to other sailings, and all disrupted passengers and freight would be cleared by midday tomorrow.
KiwiRail operations general manager Iain Hill said he fully appreciated passenger and customer concerns, given the time of year, but "safety must be paramount".
"As always the team worked quickly to identify and resolve the issue and minimise disruption to all customers," he said.
"In a 24/7 operation such as this, mechanical issues do occur from time to time and in that respect Interislander is no different from other transport operators.
"Our reliability levels are currently at 97.2 per cent for the fleet, with Aratere at 97.4 per cent," Mr Hill said.
He said that of the 4239 sailings scheduled over the last twelve months, 97 per cent had been completed on schedule, where weather was not a factor.
Aratere was put out of action when it lost a propeller on a crossing in November last year. It then underwent a three-month refurbishment in Singapore.
