Counties Manukau DHB was forced to replace an aging machine after it repeatedly broke down and froze while women were undergoing breast biopsies.
However, the south Auckland health board insists the faults do not reflect wider equipment issues.
According to a DHB spokeswoman the faulty machine, a 2009 model that would "break down regularly and freeze during biopsy procedures", was replaced in September 2018.
But minutes from a meeting of elected board members, held in late October 2019, show this was not the last of the breast service's equipment issues.
Another biopsy-capable mammography machine, purchased in 2010, was also showing "signs of aging and similar faults".
However, an oversight meant the machine was left off capital replacement lists due to the absence of a schedule of breast service equipment on the DHB's asset register.
During the October board meeting, elected members noted replacing the 2010 model was "urgent".
The machine was "past its useful life and regularly breaks down", they said.
"This puts the service at risk as during downtime for this machine there is only one biopsy capable machine left in the department to support the busy clinics," meeting minutes read.
Eventually, in January this year, the 2010 model was replaced. It came several months after fears were raised the breast imaging service would be left with only one reliable biopsy machine.
"As much of the clinical equipment in the breast service is specialist equipment that is maintained and repaired by external technicians, this resulted in an oversight," the DHB's spokeswoman said.
"The BreastScreen Service has worked with our clinical engineering team to ensure they have a full list of equipment to prevent this occurring in the future."
Despite the oversight, the DHB was not concerned other replacements would be missed due to absence from the asset register.
Its spokeswoman said individual services were aware of equipment that needed replacing and there was a clear process to apply for items left off replacement lists.
CMDHB also said problems with the biopsy-capable machine purchased in 2009 did not reflect a wider issue, namely providing reliable equipment while staying within budget constraints.
The 2009 model was used "rarely" and as a "backup" when clinics were "very busy", the spokeswoman said.
"The freezing during biopsy procedures occurred around 2-3 times and in all in these cases the patients were able have their procedures completed on the day of their appointment."
Meanwhile, demand for the services of the DHB's breast clinic is expected to increase.
For now, wait times for women to be seen at the clinic are continuing to exceed targets due to capacity issues.
Missed targets result in "clinical risk", health board papers showed, seen through the delayed diagnosis of 35 women in 2019.