I just got a glimpse of this, and it may either be a blooper or a mistake on my part! When they first show the grave (4-5 minutes into the episode) there is no tree or bush behind it. Near the very end, they show it again, and now there is a tree or bush behind it. Thanks Renewed Fan!
The date on Sam Elder's marker for his grave was 1871 which is far too early (Mark would have been born pre-Civil War). In the 2nd season episode Martinet episode #83 the date on the grave was 1883 or 1884. Thanks Renewed Fan!
After Sam Elder dies in the middle of Main Street in North Fork, Lucas and Mark are standing by as Tim Elder buries Sam (his father)... the dates on the grave marker are 1820-1871. Impossible since Lucas and Mark rebuilt their home in 1881!
When Lucas climbs off the ladder to stop Mrs. Claremont’s horse, Razor is not by the house. (There is a horse in the background, but it looks too light to be Razor.) After Mrs. Claremont shows Lucas the articles her husband wrote about him, Lucas walks to the hitching post in front of their house. Mounts Razor and leaves in a hurry! (This riding away scene is stock footage from Boomerang.) Thanks Ann Marie!