Audio problem: Billie says her line "he needs a new image" without moving her lips.
Audio problem: In the final song, "This is What It's Like to Be Lovers", the lead male studio singer starts the song, not David Cassidy, then they switch to David Cassidy's real voice halfway through for just two lines, then they switch back to the male voice of the studio singer.
The Great Voice Robbery - S1-E3
Audio problem: Several times throughout the episode while the characters are speaking in other people's voices the spoken words don't match the lip movements.