The investigation findings come about three years after the man's death. Names have not been published in the report for privacy reasons.
While the man lived at the rest home, he developed serious pressure wounds and was hospitalised for urinary tract infections (UTIs).
Deputy Health and Disability Commissioner Rose Wall suggested these hospitalisations could have been avoided and that he may not have deteriorated so rapidly had effective actions been taken.
She said clinical assessments, documentation and plans to mitigate the risk of his injuries were inadequate.
Wall recommended that Oceania arrange training on resident care planning and pressure area risk assessment and management.
The deputy commissioner also ordered an audit of long-term person-centred care plans and monitoring forms.
Facility staff were also told to apologise to the man's family.