Broken Link - S4-E26
Revealing mistake: During the fight between Garak and Worf near the end of the episode, a Jefferies tube door is knocked out of its frame to reveal the end of the set - a dark room with a wooden scaffold and various other pieces of equipment (slow-mo helpful but not required). (00:36:00)
Food Fight - S1-E6
Revealing mistake: When Pudgy Pig is standing outside of the food packaging plant, a human hand can be seen sticking out of Pudgy Pig's wrist. (00:15:30)
Revealing mistake: The stick of dynamite Brisco throws lands to the right of where the pyrotechnic for the dynamite explodes.
Revealing mistake: About 20 minutes in, the cops have a newspaper with the headline about the two guys they killed. They turn to page two which has a story about the next guy they are planning to kill. If you look at the picture, it is glued onto the story page. The left side is lifted. The actor must have been hired after the printing.