The beleaguered Interislander ferry Aratere has been cleared to sail again tonight after the vessel suffered yet another technical fault today.
KiwiRail said the fault was discovered as the ship was preparing to berth at Wellington just before 2pm today.
While the vessel was still fully operational and had berthed safely, Aratere's 2.45pm sailing from Wellington to Picton was cancelled to allow time to identify and repair the fault.
The ferry's 6.45pm crossing from Picton to Wellington was also cancelled.
In a statement tonight, KiwiRail said a number of alarms had showed up on the control screen in the engine room as the vessel was approaching Wellington, even though the vessel was operating normally.
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.