The Way of the Warrior (2) - S4-E2
Character mistake: During the Defiant's flight to save the Cardassian officials, Worf says something to the effect of, "I've never been aboard a Federation ship equipped with a cloak before". However, he was aboard the Enterprise during the Pegasus incident, where The Ship was temporarily equipped with a cloaking device.
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.
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?