The clock in the kitchen when Judy visits Sid at the beginning never moves from 1:18.
Garland was not replaced by British singer and entertainer, Lonnie Donegan. She fulfilled her five-week booking at The Talk of the Town (at a fee of £2,500 per week, the equivalent of £48,000/$62,000 p/w in 2024.)
Lorna and Joey Luft are shown as small children in the movie. The movie takes place in 1968/1969 which would've meant that Lorna would've been 16 or 17 during that time and Joey would be around 13 or 14.
Lorna and Joey Luft were living with their father at the time movie is set.
Judy Garland did not meet Mickey Deans at a party. In real life, he met her when he was delivering some of her drugs that she needed to function in life. He was introduced to her children as Dr. Deans when he showed up at their door.
During the first song when Judy performs in the UK, the drummer pretending to play drums hits one cymbal continually and it actually falls off the cymbal stand.
When Judy and Mickey make a tower of cans above their sleeping friend, one of the cans is a state 7-Up can, released in 1976 for the U.S. bicentennial.
When Judy calls America from a phone booth, she only puts in a few coins at the beginning of the call. In 1969, a phone call to the USA was extremely expensive from a phone booth, and she would've had to add more coins constantly.
Judy asks Mickey Rooney a question and he begins his answer with the word "So,...". Prefixing an answer like this is a 21st century affectation and would never have been done in the 1930s.
In the restaurant, when Rosalyn & Burt take Judy for cake, she eats with her right hand. Judy Garland was left-handed, as shown earlier in the montage when she is signing autographs.