Character mistake: When Troi is talking with Picard and Dr. Crusher about what's wrong with her mother, she says that "something was happening in her metaconscious mind." Dr. Crusher then asks "metaconscious?" As a Star Fleet doctor, she's had to study the neurology of Betazoids, Vulcans, and other telepaths. She should be familiar with the concept. (Yes, it's expository dialogue for us, the audience, however, Picard is in this scene too and it would have made more sense for him to ask about it.) (00:17:55)
Continuity mistake: Lwaxana and Deanna get in an elevator and Deanna tells it to go to Deck 8. But when they arrive the sign says 12 Turbolift.
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.