Audio problem: When Riker leaves Deanna and Wyatt at the holodeck you hear the door. You don't hear it a minute ago, when Wyatt enters the holodeck - he just appears. (00:27:30 - 00:28:15)
Audio problem: Near the end, when Leech points his gun at Crusher, there is the sound of him cocking the weapon. However, when we see his gun immediately thereafter, the hammer is in the uncocked position.
When The Bough Breaks - S1-E17
Audio problem: Riker's lips don't match what he is saying when we hear Riker's statement of being surprised when Tasha hasn't heard of the stories of Aldea.
Audio problem: After the offer of refreshments has been declined, Harmony says "I have been expecting you", but her mouth doesn't move.
Audio problem: We hear Reva's female member of his choir say "I have been expecting you", but her mouth doesn't move.
Audio problem: In Engineering when Worf says "Ensign," Michael Dorn's lips don't move. (00:22:35)
Bloodlines - S7-E22
Audio problem: When Jason is having seizures in his quarters, Dr. Crusher gives him an injection to stop it. But watch Jason closely - he goes limp BEFORE you hear the sound of the hypospray.
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.