The One With Ross's Wedding, part 2 - S4-E24
Audio problem: Toward the end of the episode Ross' Dad and Emily's dad are arguing. Ross comes between them and you can hear the audio saying"From now on everybody gets along!" But it does not match up with the movement of Ross' lips.
The One After Ross Says Rachel - S5-E1
Audio problem: Monica tells Ross that he should keep looking for Emily, and Chandler says "Yeah, for about 30 minutes." But the audio doesn't match up with his lip movements, indicating this line was dubbed. (00:10:26)
Audio problem: When Rachel and Ross are in Central Perk, Ross says "Well there's this one thing." Then it cuts to a shot of the side of his head where he says "Okay" and it doesn't match his lips.
The One With The Ball - S5-E21
Audio problem: When Rachel is trying to sell the cat and someone looks the hiss is a clear overdub. (00:16:20)
The One With Joey's Big Break - S5-E22
Audio problem: At the very end when Ross hits Rachel's stomach twice the sound doesn't match his actions. (00:21:00)
Audio problem: Right after Ross and Rachel leave the wedding chapel, Joey and Phoebe rush in. Joey is saying "C'mon, Pheebs, hurry, hurry." and she is saying "Okay, okay." However, neither one is moving their lips. (00:00:25)
The One Where Ross Hugs Rachel - S6-E2
Audio problem: In the pre-theme-song scene, with Phoebe and Ross talking outside the coffeehouse, when Phoebe sends Rachel away in the cab for the second time the sound of the tyres screeching starts while the cab is still stationary.
The One Where Ross Got High - S6-E9
Audio problem: When Ross and Joey go into the bedroom, you can hear the duck in the background, even though the chick and the duck should be in the other apartment and aren't even in this episode. (00:12:53)
The One With The Routine - S6-E10
Audio problem: When Ross has finished telling everyone the story of the dreidel, we cut to Monica and Chandler's reaction shot which shows Ross' mouth moving even though he is not talking. (00:01:30)
The One With The Apothecary Table - S6-E11
Audio problem: When Phoebe puts her feet up on Ross' apothecary table, Ross asks her not to put her feet up on his "new...old sheet." During the pause right after he says "new," there's a cut to a different angle and you can see his mouth form the words "old sheet." Then it cuts to a different angle and we actually see and hear Ross say "old sheet." (00:12:05)
The One With The Proposal, part 2 - S6-E25
Audio problem: In the pizza place, after Chandler tells Monica to "put down [her] copy of The Rules..." you hear Monica say, "You know what. I gotta go" when her lips aren't moving. (00:04:26)
The One With Monica's Thunder - S7-E1
Audio problem: When Joey walks out of the bedroom dressed as a 19 year old, when Chandler says the line "Yes, on a scale from 1 to 10, 10 being the dumbest a person can look, you are definitely 19", you can see that the audio doesn't match the words. It looks as though Matthew Perry says "not 19" and they had to re-dub over post production with "19." Subtle, but it's there. (00:08:50)
Suggested correction: Just watched it twice and seems to be fine... Can't see any issue.
The One With Rachel's Book - S7-E2
Audio problem: Chandler, Monica and her parents are at dinner to discuss the upcoming wedding. When they describe how they remodeled the kitchen when she broke up with Richard, the camera pans to Monica and her mouth is moving but there's no sound. It then switches camera angles and Monica audibly asks, "Well what about when I started dating Chandler?" Which is what she said in the frame before with no sound. (00:11:00)
The One With Ross's Library Book - S7-E7
Audio problem: When Janice is groaning about Clarke sanding her up, the second "Oh" is obviously pre-recorded and the third "Ah I j..." is audio from the next closeup shot that hasn't been cut to yet. On top of this, her mouth moves on neither of them. (00:12:15)
The One With The Truth About London - S7-E16
Audio problem: During Rachel's scene sitting on the couch with Ben talking about her and Ross and her sisters, Rachel's mouth moves in any scene showing Ben, but without her being heard.
The One With The Red Sweater - S8-E2
Audio problem: When Joey is proposing to Rachel and he tells Phoebe to give him the ring back, she says "No!" and pulls her hand away. When she pulls it away, she hits her chest and there's a thump sound that's clearly the sound of her clip on microphone being hit (it's way too audible to be just a thump on her chest). (00:17:50)
The One With The Video Tape - S8-E4
Audio problem: When Joey says "this is not fair to her, let's just forget the tape", his mouth stops moving after he says "forget", making it look like the audio is coming from nowhere. (00:12:07)
The One With The Halloween Party - S8-E6
Audio problem: When Rachel greets Mona at the door of the apartment, visually she says "Hi" but the audio is " Hi Mona. "
The One In Massapequa - S8-E18
Audio problem: When Monica is preparing her speech, she stands up to show Chandler her note card, but when you can hear her say "Hey, check this out," her lips don't move. (00:02:20)
The One Where Rachel Has a Baby, part 2 - S8-E24
Audio problem: As the nurse comes back from wrapping the new baby, we hear her say "Here she is," yet her mouth doesn't move to the words she is apparently saying. Even though her mouth is only visible during the "she is", she's not saying the words. Then she mouths some sort of "oh", but nothing is heard. (00:09:00)