A Simple Investigation - S5-E17
Revealing mistake: When Odo and Arissa are talking in Odo's quarters, you can see where the star field ends and where the sound stage floor begins. (00:22:40)
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)
The Way of the Warrior (1) - S4-E1
Julian Bashir: They broke seven of your transverse ribs and fractured your clavicle!
Elim Garak: Ah, but I got off several cutting remarks which no doubt did serious damage to their egos.
If Wishes were Horses - S1-E16
Trivia: Buck Bokai's baseball card, a collectible featured on Benjamin Sisko's desk, had actor Keone Young on the front, in character, but showed "Trek" model maker Gregory Jein, who invented the "history" of the character, on the back. The pair bore an uncanny resemblance to each other.
Emissary (1) - S1-E1
Question: Did Nana Visitor's hairstyle change from her first appearance in the episode to the next scene when they were going down the stairs?