Barnabas attacks a television during a live performance of The Carpenters singing "Top of the World." The song was originally released in 1972, on the album "A Song For You," but it wasn't released as a single or performed before a television audience until 1973.
The train Victoria rides during the opening credits is the Amtrak "Downeaster", which started service in the early 2000s. The cars and engines are from the 1990s, with the post-2000 Amtrak logo. When Amtrak was formed in 1971, the trains had rusty, hand-me-down streamlined passenger locomotives and cars that were near the end of their lives.
The architectural style, detailing and furnishing (e.g. a piano) of Collinswood - which Barnabas and Angelique recognize from c. 1776 - are wildly out of character for that period, and characteristic of the mid- to late-19th century, rather than the 18th.
The song "Crocodile Rock" is heard. The year is 1972, possibly fall. Yet this song wasn't released in the United States until November of 1972, making it unlikely it would be in a jukebox in a backwater town like the one presented.
When Angelique visits Barnabas at his home for the first time after his return, they move to the drawing room. Angelique reclines on the sofa, and the inside lining of her right boot is visible. In the next shot, the lining has been reinserted into the boot, but it appears and disappears continuously in various shots where the top of her boot is visible.
On the Amtrak train, the poster where "Victoria Winters" takes her name is for skiing in Victoria, British Columbia. Victoria is on Vancouver Island at the southern tip of BC. With its temperate climate and lack of mountains, it is not a ski destination (unlike Whistler BC, for example, which is on the mainland, and benefits from the Rockies).
In 1776, the American Revolution was in full swing. At the same time Maine was the name of a cultural region, which was legally part of Massachusetts rather than a separate colony/state in its own right (and remained so until 1820). It's odd that neither of these facts came up at any point during the 1776 part of the story. Surely they would have merited at least one line apiece at some point.
When Maggie Evans arrives at Collinswood, her first conversation with Willie indicates that she has applied for the governess job under the name Victoria Winters. An earlier scene shows that she didn't invent the name until earlier that same day, on the train en route to Maine.
Towards the end, when Angelique and Barnabas are in her office, the door opens, and Barnabas is chained into a coffin. The lid is separate. Later, when Angelique opens and closes the coffin, the lid is on hinges.
When Angelique goes to look at the site where the Vampire has killed the workmen, she is wearing long black pants. In the Collinwood driveway, she is wearing black tights and high heel shoes. When she enters the house, she is wearing long black boots.
When the townspeople bury Barnabas in 1776, a man with very distinctive long, blonde hair with some dark patches is on Angie's left. Barnabas was buried for 196 years. The same man appears in a 1972 scene showing the restoration of Collinwood. He appears at the start of the scene, as a workman in gray overalls, walking from left to right behind the car Willie is polishing.
When the townsfolk and the police cars have rushed to the Collins' mansion and Barnabas start to fight the witch, the background scene is a photograph of the townsfolk being held back by police. Similarly, before that, as the townsfolk are chasing Willie (in his car) away from the burning cannery, three firemen are frozen in the background, down a side street - evidently a picture again.
In the final scene after Victoria falls, Barnabas has bitten her to make her immortal and the blood leaked out of his mouth. When Victoria kissed him after that and put her hands on his face, the blood has not been wiped and is still sticky to Barnabas' skin, proving that it was make-up.