Diverse had cited "dishonesty" and "serious or repeated failure to follow a reasonable instruction" as reasons for firing Clement, who the business said "misused" his work time.
The allegations were based on five separate incidents where Chandler had spotted Clement's work van at his workshop near Diverse's premises when Chandler had expected Clement to be at home sick or out visiting clients.
Diverse said Clement didn't have permission to be at his workshop on the occasions and therefore had been dishonest and failed to follow instructions.
But the ERA said the company couldn't prove Clement's actions had been dishonest because it had failed to properly investigate what Clement had been doing when his work van was parked there.
The authority added it was unfair and wrong of Diverse to conclude Clement had repeatedly ignored an instruction not to go to his workshop during work time because Chandler could not recall telling Clement not to go to his workshop during work time until after he gave him a second warning for doing so.
Chandler never went inside the workshop to see what Clement was doing on the days he saw the vehicle parked there without permission.
The first time Chandler saw the van at the workshop when he believed it shouldn't have been was on October 20, 2015 after Clement had walked out of the office an hour and a half after starting his work day after a heated argument with a colleague.
Chandler said he had expected Clement to go home but saw his van at his workshop hours later.
The next day Clement arrived at work at 8am and said his throat was sore. Chandler said he could go home sick.
But hours after Clement left the office Chandler saw his van at his workshop. He had expected Clement to be at home.
The next day he called Clement in for a meeting and gave him a warning letter which stated Clement had logged eight hours' sick leave on his time sheet for his absence on October 20 and that this was a breach of his contract because he hadn't been off sick that day.
But the time sheet, which was submitted to the ERA as evidence, actually showed that Clement had claimed eight hours' sick leave for October 21 and had correctly put down that he worked an hour and a half on October 20.
On December 9, 2015, Chandler again saw Clement's van at his workshop when he was meant to be visiting clients.
He phoned Clement and asked why he had been at the workshop when he was supposed to be working.
Clement said he hadn't been and had been out seeing clients as instructed.
Chandler never told Clement he doubted this because he saw Clement's van at his shed. He also didn't check with the clients whether Clement had visited them that day because he didn't know who the clients were and didn't ask Clement for their names.
The next day when Chandler again saw Clement's van parked at his workshop when he was supposed to be out seeing clients he phoned Clement and asked where he was.
Clement said he was "at Trafalgar Painting doing a call".
Chandler then asked Clement to go back to the office to do paperwork.
When Clement arrived Chandler asked why, if he was seeing clients, was his van at the workshop.
Clement said he had left the vehicle at the shed and then had walked to see clients.
Later that afternoon Chandler called Clement into his office for a disciplinary meeting and gave him a written warning - his second - which he had prepared the day before and outlined Chandler's concerns about where Clement had been on December 9.
By issuing the warning before giving Clement a chance to explain why his vehicle was parked at his workshop Diverse had failed to act as a fair and reasonable employer, the ERA said.
When Chandler fired Clement on December 23 after he saw his van at the workshop again without permission, and called him in for another disciplinary meeting he gave Clement a typed up dismissal letter.
The ERA said a fair and reasonable employer would have allowed Clement to explain himself during the meeting before deciding whether to fire him.
The authority also said the company shouldn't have taken the first warning letter into account when deciding whether to fire Clement because it incorrectly said he had falsified his time sheet for October 20.
It concluded Clement was unfairly dismissed and ordered the company to pay $29,231.56.
