During the ERA hearing Affco's executive director Dane Gerrard submitted that he wanted to "underline the serious threat of union intimidation that was occurring in the factory at the time.
"The issue is about intimidation of other staff not wishing to accept a strike declaration from the union after certain employees had already declined to accept, which is their right."
But ERA member Andrew Dallas said Mr Gerrard's concerns did not change that the Employment Relations Act required the Authority to consider if the company's decision to dismiss was correct.
Affco's operations manager Tony Miles, who conducted the investigation, found his actions were so serous he had no option but to dismiss him.
The ERA found Mr Miles had formed a view that Mr Harris was responsible for the vandalism and had closed his mind to the possibility it had been caused by somebody else, so did not properly investigate the allegations. Northern Advocate