Glitter Rock - April 12, 1974 - S3-E17
Other mistake: During the album signing at the mall, a woman exposes her breasts to Sam. We see her from the front with Sam's hat covering her breasts. His hat moves just enough that you can tell she is wearing something covering her breasts.
A Hunting Will We Go - June 18, 1976 - S3-E18
Other mistake: The episode takes place in Arkansas, but at one point Sam is in a telephone booth and very tall mountains are behind him. Arkansas doesn't have snow-capped peaks.
Last Dance Before An Execution - May 12, 1971 - S3-E19
Continuity mistake: When Sam is strapped into the electric chair, the huge clock on the wall behind him, which is there so that both the prison doctor and the reporters viewing the execution can mark the time of death, reads 7:00. The final scene runs for more than five minutes - after which the clock still reads 7:00. (00:37:15 - 00:42:00)
Last Dance Before An Execution - May 12, 1971 - S3-E19
Continuity mistake: As Sam is marched down the corridor to the electric chair, Raul reaches through the cell bars and begs him to confess. In long shots, Raul's arms are fully extended. But in close-ups, his arms are folded and wrapped around the bars. (00:38:30)
Nuclear Family - October 26, 1962 - S3-E21
Audio problem: Just before the dog carries in the sack of shotgun shells, Mack and Sam have an argument, and Mack's dialogue is very poorly looped. Throughout the scene, the sound is out of sync with his lip movements. (00:33:00)
Chosen answer: Per the Quantum leap page at http://www.scifi.com/quantum/episodes/season5.html. 8 August 1953: An enigmatic leap lands Sam in a Pennsylvania tavern, as his own grown self on the day of his birth. As Al and Gushie work frantically to locate him, Sam befriends a wise bartender (popular character actor McGill, who'd appeared in a different role in the very first "leap") and a group of coal miners. As a host of familiar-looking faces pass through the bar - with different identities than Sam remembers - Sam ponders his life of leaping with Al the bartender, who tells Sam he controls his own destiny. Pressed for more, Al the bartender simply shrugs and says, "Sometimes, 'that's the way it is' is the best explanation." Sam realizes he must right at least one more wrong before he can go home, and leaps back to tell Al Calvavicci's wife Beth (from "M.I.A.") to wait for Al, who will survive Vietnam and come home to her. The closing title cards state that Beth and Al have four daughters and will shortly celebrate their 39th wedding anniversary ... and that Sam Beckett never returned home.
Boobra