The object that Patsy cuts in the kitchen changes from a cake to a pie.
The movie shows the car her brother was driving being broadsided by a truck, when in fact it was a head-on collision with a car coming the other direction. Patsy was thrown through the windshield, not pulled from the wreck by her brother.
The primary cause of the plane crash that killed Patsy is shown to be engine failure. The FAA investigation conducted after the accident found no issues with engine or propeller. The cause of the accident was determined to be navigation error and pilot disorientation.
There's a scene where they play "Stranger On the Shore," which came out in 1962. The scene is some time before then.
Shortly after Charlie gets drafted into the Army, Patsy drives to Fort Bragg to visit him. When she arrives at the main gate, she asks the Military Police guard for directions to Charlie's barracks. The guard gives her the directions, then immediately waves her through the gate without asking for any identification. In the real Army, Patsy would never have been allowed to enter without showing a valid photo ID card.
When Patsy and Charlie are dancing at night outside the bar in heavy rain, the "rain" is obviously fake. Also, neither of them gets wet.
In 1957, Patsy is shown listening to Elvis' "Can't Help Falling in Love" on the radio, which wasn't a hit until 1961.
In a scene dated 1959, Patsy is performing in a drive-in theatre when a Sprite commercial appears on the screen. Sprite was not introduced until 1961.
After Patsy has her baby and returns to singing, there is a scene where her mother is bottle feeding the child in her car, using a pink Gerber plastic bottle, which wasn't available until the 1970s.
The guitar that the singer/MC is using on the "Opry" stage is a Fender acoustic, not available until at least 1966.
A white 1963 Cadillac convertible is seen parked at Patsy and Charlie's house on the day they are giving a graduation party to Patsy's sister. It was the day of Patsy's accident which was 14 June 1961.
When Charlie is riding his motorcycle under the bridge on his way home to see Patsy in Winchester, VA (but filmed in Martinsburg, WV), he is actually going in a direction that is "leaving" Martinsburg, WV, not entering it.