The phone number that Patrizia writes in lipstick on Maurizio's windshield changes between shots.
When Patrizia and Pina sit outdoors with the two hitmen, Patrizia leaves and snatches her packet of cigarettes as she goes. In a following shot, as Pina gets up to leave, the packet is back on the table.
After Paulo Gucci gets out of his car to confront Maurizio Gucci and Patrizia Reggiani, the length of his cigarette keeps changing.
Paola's cigarette changes from left to right hand, then back to left, when Patrizia confronts her at the table.
The movie deliberately begins 8 years after Patrizia's and Maurizio's relationship began in reality. Therefore, it makes the birth of their daughter Alessandra also chronologically incorrect; in reality, she was born in 1976, which is 2 years before the year that her parents first met in the movie.
The very final scene solemnly lists the prison sentences handed down to each conspirator, but includes this glaring spelling mistake:
"Benedetto"recIEved a life sentence"
When Aldo visits Rodolfo knowing the marriage of Maurizio (1972), Aldo proposes a plan to have a branch at a mall that will open soon in Gotenba, Japan. In 1972, the lot of the future mall was a vacant land. In 1974, a theme park opened as Gotenba Family Land. The park was shut down in 1999 and was replaced in 2000 by Gotenba Premium Outlet, 28 years after the discussion. A branch of GUCCI is there indeed.
When Paola listen to a Brazilian song, she mentions that it reminds her of Ipanema, a famous Brazilian beach. Then she starts to dance and asks Maurizio if he knows how to dance salsa.
Salsa is not a Brazilian dance, it is a Cuban dance.
In a Christmas scene set in the mid-1980s, a character gives a gift card. They first appeared around then, but didn't become mainstream for several years. The gift card is intended to highlight the characters' exclusive tastes.
(at around 34 mins) When Paolo is taken down playing rugby, Jared Leto's bald cap falls off of his head, revealing the long dark hair underneath.
When Aldo is washing dishes in Paolo's kitchen, the supposed neon tube over the sink is an unconcealed modern battery-powered Astera LED light predominantly used for filming purposes.
When Maurizio Gucci is doing the photo-shoot a Hasselblad medium format camera without automatic winder is used. Fast continuous shooting as shown would not have been possible with this equipment.
In one Milan city shot, a street sign says "controllo elettronico", meaning there is electronic control of parked vehicles. The system was introduced around 2000.
Patrizia has a Walkman cassette player in 1978. Sony introduced the Walkman in 1979.
The film opens in 1978, and Patrizia dances to "On the Radio" at a party. The song was released in early 1980.
In 1983, at the Versace Fashion Show after party, the song Paid In Full (Cold Cut Madness) by Eric B. & Rakim plays in the background. The song was released in 1987.
When Maurizio introduces himself to the man after the Gucci show, his mouth does not move.
In the nightclub scene with Bobby Short (out of focus in the background), his lip-syncing is out of sync with the sound track.
In the first scene with Aldo and Rodolfo talking in the garden, the film crew can be seen in Aldo's sunglasses.
Shortly after their wedding, Patrizia and Maurizio are invited to Aldo's 70th birthday party. Several years later, Aldo is arrested for tax evasion. When Paolo and Maurizio are on the phone discussing the arrest, Paolo says, "My father is 70 years old." His father actually would be several years older.
The Italian accent is completely wrong. They make it seem like the whole family and Patrizia as well are from the south of Italy, while they were respectively from Tuscany and Milan.