When Werner Klemperer puts his hands on the closed ledger on the miners who have been killed, the ledger reads "Comstock Personal" instead of "Comstock Personnel" as it did when the book was opened, earlier.
When Bret returns to check the door for a bullet, after he verifies that the hinge is tampered with he opens the door. It clearly has the name Bordeen on it, just like it did earlier. The closet door he finds the bullet in does not, and didn't previously, have Bordeen's name on it.
Bret manhandles Ellen in an effort to get her to return his money. In doing so, he shoves her against a wall, which wobbles ever so slightly, demonstrating that it is not a solid wall in a building, but a temporary wall on a stage set.
When Bret Maverick and Ellen Bordeen are on their picnic a crew's shadow can be seen moving on the buggy behind Maverick.