Inquiries also revealed Capital & Coast DHB launched an investigation into alleged inappropriate sexual behaviour by one of its doctors but did not find any "corroborating evidence".
Hawke's Bay DHB investigated one report of bullying, another of harassment and an allegation that a staff member had sworn and yelled at a colleague, but it did not reprimand anyone in relation to the incidents.
The revelations come as nurses around the country are threatening to strike for better pay and working conditions.
They echoed a 2015 study by Massey University management researcher Dr Kate Blackwood which found that only one of 34 cases of bullying among nurses at New Zealand hospitals was fully resolved.
Other research, conducted by the Association of Salaried Medical Specialists (ASMS) last June, found a third of senior doctors and dentists surveyed said they had been a victim of bullying and two-thirds had witnessed bullying. Of those who were bullied only a third reported it.
CultureSafe NZ director Allan Halse said the leaders of many DHBs did not understand the potential harm bullying caused. He added bullies were often in management positions because they were good at the technical aspects of their jobs.
An overhaul of DHB workplace culture was desperately needed but that would only happen after a crisis, Halse said.
Under the Health and Safety at Work Act 2015 employers could be held liable if an employee took their own life due to workplace bullying.
"For it to change somebody has to die and a chief executive has to be jailed and then they'll take it seriously," said Halse.
Blackwood said bullying was often subtle, such as withholding information, giving staff excessive workloads, gossiping and spreading rumours.
"Because bullying is defined as a build-up of behaviours over time, it's really hard for a victim of bullying to get sufficient evidence to substantiate a complaint," she told the Herald on Sunday.
Employment lawyer Catherine Stewart said workplace bullying and harassment could affect morale of the wider team as well as victims.
She also cited multiple cases where several victims of bullying had come forward after one person laid the first complaint.
Employers should investigate claims of bullying and harassment thoroughly and interview all parties and any witnesses, Stewart said.
"If a business does not act to address bullying concerns, that can undermine the trust that staff have in the employer, although the employer can also be constrained by confidentiality from discussing matters widely.
"In our cases we observe a correlation between bullying and the emotional and physical health of staff, with bullying situations often leading to increased sick leave and high staff turnover."
Nurses' Organisation spokeswoman Lesley Harry said DHBs dealt with bullying and harassment on a case-by-case basis and all staff and managers would need to work together to stamp out the problem.
The union advocated for nurses who were not satisfied with how their employers investigated complaints of bullying and harassment.
ASMS deputy executive director Angela Belich said its members were seriously concerned about bullying and harassment but it was confident DHBs took the issue seriously.
Not all instances of inappropriate or unprofessional behaviour in the workplace required disciplinary action, she said. Instead, restorative practices, training and professional development were sometimes more effective ways to resolve bullying and harassment.
Both Hawke's Bay and Capital & Coast DHBs said they had zero tolerance for bullying and harassment and investigated allegations thoroughly.
However, the boards refused to provide further details on the inquiries they made into the 2016 allegations due to privacy concerns.
The Southern and Nelson Marlborough DHBs did not respond to Herald on Sunday questions about their harassment and bullying inquiries by deadline.
A spokeswoman for Auckland DHB said it had introduced culture change initiatives to tackle bullying and harassment, including educational programmes for managers, and an anonymous help line for victims, during the past few years.
"Our long-term goal is to prevent bullying and harassment, as well as manage it when it might occur. We're making good progress, but acknowledge we are only at the beginning of the change of culture that will eliminate bullying," she said.
