The Auditor-General's office is also investigating.
Mr Sharpe injured his neck and shoulder in 2008 while lifting his stepson onto a top bunk. ACC has paid him for two operations, and he is still on weekly compensation because of pain for which he takes painkillers every four hours.
But he has had to get ACC decisions in his case reviewed six or seven times and is now taking the corporation to court to get it to pay for a recent shoulder operation that his private health insurance had to pay for.
"I'm still trying to get my left shoulder covered, even though it's obvious it [the pain] is from the original accident," he said.
He has requested copies of his ACC files several times since the accident.
The wad of papers he received yesterday was his file for just the past 16 months since he last requested a copy in March last year.
Ms Pullar said Mr Sharpe's case showed that the documents she received were not an isolated case.
Outgoing ACC chief executive Ralph Stewart said the latest case was "human error".
"The mistake in the information was discovered and corrected in the client's electronic file, but overlooked in the large paper file that was released," he said.
"Since the much publicised breach earlier this year, ACC's polices and processes relating to the handling of client information were reinforced. Privacy training was undertaken by all staff, and those managing personal client details signed an agreement committing to best practice management of personal information in their care.
"There are systems in place to physically check all personal information before it leaves ACC.
"An internal investigation is under way into the circumstances of the breach and the errors that led to it. We have contacted both clients involved and are in the process of retrieving the information ...
"The Office of the Privacy Commissioner has been notified."
He said ACC would implement all recommendations that emerged from the KPMG/Integrity inquiry.