In the early scenes, when Freddie Beenstock's father is eyeballing Jim Heeler and Henry Hobson, through his window, on their way to Moonraker's Pub, the "Beenstock & Sons" lettering is painted on the middle panes of the colonial type windows and are aligned with Mr. Beenstock's chest and waist. Just a few frames later, when Freddie joins him, the lettering has moved to the top panes and is aligned with their heads.
In the scene at the beginning of the film when Hobson is at the bottom of the staircase, the shot shows a mat or carpet at the top of the stairs. Hobson runs up the stairs and the shot showing him saluting at the top landing, shows no mat or carpet at all. Only a bare floor.
When the opening scene goes inside the store, it pauses to show the front door, complete with the blind rolled down. A little later Hobson lets himself in but the blind on the door is now up.
Willy Mossop places his belt on top of his jacket whilst undressing on his wedding night. Moments later he is called into the bedroom and picks up his trousers and jacket, but his belt is missing.
On New Year's Eve when Will returns home moments after Maggie, he closes the entrance door; but it doesn't remain shut as he descends the stairs into the shop/living quarters.
When Will sets to work on the large, pristine piece of leather, he commences marking from the middle. Calculating from the middle would waste valuable leather; one would begin figuring from either end of the sheet.
When Maggie and Will are standing outside the church before their wedding, a cooling tower can be seen to the left of Maggie. It would not have existed in 1800's Salford.
The first coal power station in the UK was in 1882. Bustles were fashionable until 1913 and the first power station in Manchester was 1893 so it may have been possible.
When Maggie and Willie leave their benefactress' house, the film crew is reflected in the shop windows as the two walk down the street.