Telecom's heavily promoted 3G mobile network has run into more problems in the lower part of the North Island.
A new outage which began in the early hours of the morning left technicians and engineers scrambling to restore services over the next 11 hours.
Mobile phone sites in New Plymouth were affected from about 3.30am, and problems were also reported in Upper Hutt and the Wairarapa.
Services were fully restored by 3pm.
A Telecom spokesman said the problems appeared to stem from linking the sites to a new radio network controller that had been installed in Christchurch overnight.
The work was stopped while the affected sites were brought back online.
The XT network had a major failure in mid-December and another in late January in which up to 200,000 customers south of Taupo were cut off for up to three days.
Telecom later said it would make $5 million worth of goodwill payments after the failure in January.
Ironically, the network upgrade which apparently triggered the latest problems was intended to make the XT links more robust.
Telecom said it had built a new radio control network in Christchurch, and overnight moved 16 sites on to it, only to have those sites start experiencing "service issues".
"Users in the affected regions will have had a degraded mobile service," the company's subsidiary, Gen-i said.
"We have rolled back those migrations, we will assess the cause of the issue and then recommence the programme."
Telecom plans to complete installation of the new network controllers by mid-March.
NZPA