The Nurse's union says mistakes with the pay back systems are costing nurses tens of thousands of dollars.
Te Whatu Ora has paid back $250m of the almost $2 billion following years of breaches of the Holidays Act.
But the Nurses Organisation says mistakes with the remediation work meant payments varied wildly.
In a statement, Te Whatu Ora said the work was taking longer than planned as they continued to add more resources across their payroll teams.
Nurses Organisation president Kerri Nuku spoke to Ingrid Hipkiss.
