Character mistake: When the artifacts from the late 19th century, found in a cave, are identified by the away team, Data identifies the pistol as a "double action" Colt 45, circa 1873. The pistol is a Colt single action army, caliber .45. Certainly not a "double action".
Devil's Due - S4-E13
Continuity mistake: As the camera does a close up on the shuttle craft's forward window as it approaches the Enterprise, the dorsal section is seen getting larger the closer they get. As Data and Picard talk, the image fades out, and a minute later, the angle changes, the dorsal section is again seen getting bigger, and the ship disappears.
Continuity mistake: At the end, Picard is looking out the window when Worf comes in. There is a plant next to Picard in the close up, but it's missing in the long shots.
Continuity mistake: Picard states that the energy beam appears to come from the deflector array, in later shots it is coming from the rear of the star drive section.
Continuity mistake: Near the end of the episode, right after Lore fires the phaser at Dr. Crusher, Data tackles Lore and knocks the phaser out of Lore's hand. The phaser flies towards the cargo transporter and when it impacts, it breaks in two. You can see a piece of it go flying off to the left. Then shortly after when Data throws Lore onto the transporter pad and Lore picks up the phaser, it's in one piece again.
Continuity mistake: In the opening sequence, the venetian blinds in Dixon Hill's office rearrange themselves between takes. They're intact after the shooting, but moments later, despite being untouched by anyone in the room, they're broken and have a huge gap in them. (00:07:00)
Power Play - S5-E15
Continuity mistake: On the planet's surface, when the away team are knocked unconscious their positions on the ground differ significantly between shots.
Continuity mistake: Just before Riker jumps through the portal with the female crew member he rescues, his phaser falls out of its holster, yet when he lands back in cargo bay 4 his phaser is right there in the holster.
Continuity mistake: On his way to the Farewell party, Picard is seen wearing his dress uniform, but no pips on it. There should be four.
Continuity mistake: Wesley says that he's departing shuttle bay 2, but on the floor, it says shuttle bay 3.
Continuity mistake: The view of the starfield in the ship's windows is always inconsistent whenever they are orbiting a planet. Sometimes the stars appear to be moving by, and sometimes they are completely static.
Continuity mistake: When commander Data is reciting the code to lock the rest of the crew out of the computer, he states the code '1-7-3-4-6-7-3-2-1-4-7-6-C-3-2-7-8-9-7-7-7-6-4-3-T-7-3-2-V-7-3-1-1-7-8-8-8-7-3-2-4-7-6-7-8-9-7-6-4-3-7-6-LOCK', but when the computer screen is shown the code reads '1-7-3-4-6-7-2-1-4-7-6-C-3-2-7-8-9-7-7-7-6-3-T-7-3-2-V-7-3-1-1-7-1-8-8-8-7-3-2-4-7-6-7-8-9-7-6-4-3-7-6-LOCK.'
Who Watches The Watchers - S3-E4
Revealing mistake: About 38 minutes into the show, when Dr. Mary Warren dies and there's a close up of Picard & Nuria, you can see the her hand moving up and down as she breathes.
Continuity mistake: In the reality where Worf and Troi are married, when she kisses his neck, all of Worf's hair has been pulled back behind his head. When he gets up and turns to face her, the hair on the right side of his head is draped over his shoulder. When the camera angle changes and Worf turns to face it, his hair is pulled back behind his head again. (It isn't Worf changing dimensions again, because he doesn't have the moment of weakness before it happens that he has through the rest of the episode.). (00:23:05)
Continuity mistake: In the early episodes, Geordi's rank is inconsistent. In "Encounter at Farpoint", he is a full lieutenant. In subsequent episodes, he is a lieutenant junior grade, before being promoted back to full lieutenant.
Continuity mistake: In one scene on the planet, Riker's clone is lying under a table fixing something and Riker is sitting in a chair talking to him. There are two camera angles used. In one angle when the clone is talking and a body double is sitting in the chair he is facing directly towards the table but in the other camera angle where you can only see Riker, the chair is at an angle facing towards where his clone is lying on the floor.
Encounter at Farpoint (1) - S1-E1
Continuity mistake: Commander Data tells Picard the Saucer Section will arrive in 51 minutes. Riker's synopsis audio can be heard in the background without interruption, and shortly after Data says this, the cameras turn back to Riker and the Video synopsis ends. Riker immediately reports to Picard who then receives the message that the Saucer Section is in orbit. Now, Riker was watching highlights of video footage from the Bridge, of which we see almost all of it because there really wouldn't be that much to view. And that's really all he could watch since we don't have cameras in the "Q-verse" and we see the footage ending with the Q sphere chasing the ship. Also, the entire ordeal was far less than an hour so there's no way a highlight reel could take an hour, not to mention the uninterrupted audio. We seem to be missing almost an entire hour. (00:37:32)
Answer: Yes. The doors to the holodecks can be locked when in use by anyone aboard the Enterprise so they couldn't be disturbed. However, high ranking officers like Captain Picard could override the doors as it's seen that overrides are in use even for the crews quarters. Even Barclay, when he's indulging in one of his fantasies could have the doors to the holodeck unlocked by an override code.