The glass entrance door to Angelos Evangelou's home was smashed in an attack which follows an assault on December 22 with firecrackers that caused extensive damage.
Evangelou was the video assistant on December 22 when Olympiakos had a goal disallowed and a penalty appeal ignored as they drew 0-0 at Volos.
The result dropped Olympiakos to second in the table and the 44-time Greek champions lodged a protest about "bad officiating" and filed a lawsuit against the five referees, accusing them of taking bribes.
They have also sent protest letters to football governing bodies UEFA and FIFA, claiming "a deliberate and surgically precise alteration of the outcome of a match in which VAR was used".
After the first attack, league referees called a strike but on Wednesday voted overwhelmingly to suspend the action after receiving assurances from the Greek football federation, the league and clubs.
There was no immediate reaction from the referees after the latest incident, and this weekend's round of Super League fixtures will go ahead with Olympiakos two points behind league leaders PAOK Thessaloniki by two points.
The football federation called the latest attack "unthinkable madness in Greek football."
Reigning champions PAOK and Olympiakos' two main rivals in Athens joined the chorus of condemnation.
"It is time for justice to speak, finally, and to find the perpetrators of these attacks," said PAOK.
AEK Athens called on the league and the government to "fully investigate all these mafia attacks", while Panathinaikos, who take on Olympiakos in a fiery derby on Sunday, said "those who resort to violence and fraud" should be punished.
Officials went on strike in 2018 when referee Thanasis Tzilos was attacked by four hooded muggers as he left his home in the town of Larissa, leaving him hospitalised with head and leg injuries.
Two years earlier the federation postponed matches after a "suspicious" fire ripped through the home of referee Giorgos Bikas.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ