An investigation by the old Department of Labour found there was insufficient evidence to prosecute and that the bolt - which appeared to have been shortened - was not an obvious hazard and could not have been spotted.
The accident led rest home owner Bupa New Zealand to remove weigh-scale hoists from its facilities.
The hoist had not been checked by its supplier since the warranty expired six years before, while the company contracted to check the device, BV Medical, did not record any faults on it aside from adjusting its legs.
BV Medical has also since introduced a new checklist process where any problems are noted with photographs and recommended changes.
But Mrs Wilson's grandson Mathew Warren said he remained unsatisfied with the Department of Labour's findings and commissioned his own investigation, and pushed for a coronial inquest.
"In the end, a statutory organisation that was put in charge of holding people accountable seems to have failed a little bit."
Having now learned an inquest will go ahead, he is hoping to use the opportunity to prevent a similar ordeal happening to another family.
Mr Warren said it was still painful for the family to know they never got to say goodbye.
"She was a 38kg woman - she wasn't a big lady - and for a hoist to fail on her in my view is unacceptable. Why did a hoist that was used every day fail so catastrophically?"
