Continuity mistake: When Loretta Lynn is at the radio station asking why the disc jockey had lied to them about playing her record, you see the picture of her that they took at home. It is a completely different pose than the one that you saw them take a couple of scenes earlier. She is looking in a different direction and she is not smiling as much as she was when they took it.
Factual error: When Loretta and Patsy return from shopping, and Doolittle gets mad about the makeup Loretta is wearing, look closely after they leave Doolittle and you will see a 1965 LeMans among the parked cars. Patsy Cline died in 1963.
Factual error: Doolittle Lynn is visiting Loretta when she is 13, which would be around 1945. The jeep he is driving is at least a 1949 model. Pre-1949 jeeps had a split windshield. Also the civilian jeep wasn't introduced until 1946, so in his first appearance he would have to be driving a military issued jeep.
Factual error: When Loretta is having her initial pregnancy exam, the doctor tells her he hasn't seen her since she was a little girl getting her measles shot. Loretta Lynn was born in April of 1932, married in January of 1948 and her first pregnancy happened soon after. The doctor scene had to take place mid- to late 1948 or early 1949. Measles shots were non-existent in those days.
Factual error: In several scenes after the funeral of Loretta Lynn's father, Duke and Loretta drive around Kentucky and Tennessee visiting radio stations to urge them to play her Honky Tonk Girl record and listening to the stations on the car radio. But the reception would be almost impossible because the 4-door 1956 Ford hardtop they are driving has no radio aerial at all on the car. For that model year, the aerial was usually on the right front passenger side of the car. I owned one so I remember.
Revealing mistake: When Loretta hears a caller from outside and then heads out to the front porch to see who's calling her name, the man coming up the hill is wearing coal mining gear. However, in the next shot, it is a different man dressed in a navy sweater and freshman's cap.
Other mistake: When Doolittle is running his jeep up the muddy hill near the beginning, the landscape changes. The hill is a straight 40° angle, but in the close shots behind the wheel, it changes to a steep 80° which no vehicle could realistically terrain, except perhaps an army tank. And he stalls out several times and has to back up, which would not happen at the 80* steep. Then he miraculously makes it over the top.