When Joe is talking to Sara Dawes near the cattle pen on her farm, he initially has his whole arm slung over the fence rail when the shot is taken from her perspective. Then the shot switches to a reverse angle, and he suddenly has only his forearm resting only on the fence.
When Mannix and Cindy are looking at the book "Holographs and History", he takes the book from her, opens the cover, and reads the name of the publisher aloud. He reads the name "P. J. Dunham and Sons" but the printed name is "P. G. Dunham and Sons".
When Mannix is showing Art Malcolm the book of rare letters at the end, the book is supposedly a collection of many different such documents, yet as Mannix flips through the pages, every page is exactly the same.