The One With The Video Tape - S8-E4
Continuity mistake: When Chandler and Monica are trying to call Greg and Jennie, the water bottles on the table move around. Phoebe and Joey didn't move them, they are drinking from the cans. (00:05:30)

The One with the Dozen Lasagnas - S1-E12
Continuity mistake: During the scene where Phoebe is telling Rachel that Paolo made a pass at her, Rachel unrolls a long length of kitchen roll. During the scene there is a shot over her shoulder where we see that the kitchen roll is as normal and in the next shot we see it unrolled again. (00:15:30)

The One With the Holiday Armadillo - S7-E10
Continuity mistake: When Ross is on the couch telling Ben about Chanukah, Ben's hair varies from shot to shot. In the first shot it's flat and in the next shot it's spiked up at the front. His hair stays spiked up for a few shots and then returns to flat. (00:06:00)
The One With The Apothecary Table - S6-E11
Continuity mistake: The red eraser knob on the magnadoodle changes from one side to the other, when Janine is going out to tell Monica she is sorry. (00:18:00)
The One Where the Monkey Gets Away - S1-E19
Continuity mistake: After Ross asks Marcel to bring him the rice, he picks up his chopsticks. In the next shot, he is holding a napkin. (00:02:15)
The One With The Video Tape - S8-E4
Continuity mistake: As Rachel goes to put the video on, Ross hangs his head. The camera cuts and now it isn't hanging. There was no time to move it between camera cut. (00:16:10)
The One Where Ross Got High - S6-E9
Continuity mistake: When Ross finishes the trifile, a small amount of whipped cream appears and disappears throughout a few shots. (00:16:35)
The One with the Fake Monica - S1-E21
Continuity mistake: When the girls are at the dance club Rachel has a watch on, and it appears and disappears throughout the scene. (00:05:15 - 00:06:15)
The One With the Male Nanny - S9-E6
Continuity mistake: When Ross storms into the kitchen, exasperated by Sandy, he is immediately followed by Rachel - but she had just been holding Emma, and there wasn't enough time for her to have given Emma to Sandy before storming into the kitchen. (00:25:00)
Continuity mistake: When Phoebe goes to the other Phoebe's house, it's raining, but when Phoebe gets into the house her hair and her clothes are dry. (00:05:00)
The One With The Embryos - S4-E12
Continuity mistake: In the last scene, Chandler is sitting on the couch in the new apartment, and the rooster is sitting on the back of the couch, with his tail facing the window. When Joey comes running out, the shot of the rooster shows his face toward the window, and then in the next shot he has returned to his tail facing the window. (00:20:45)
The One In Barbados, part 2 - S9-E24
Continuity mistake: In The One In Barbados, part 2, when Ross and Charlie are hiding behind the plant from the other scientists, the drinks they are holding refill themselves and Charlie's ornament in her drink keeps switching sides of the glass. (00:45:10)
The One With Ross' New Girlfriend - S2-E1
Continuity mistake: When Paulo comes out of Rachel's bedroom to greet the group, the robe he is wearing is obviously untied and hanging open. After we see how everyone reacted to him being there, we again see Paulo but now the robe is securely tied even though neither he nor Rachel changed positions between shots. (00:11:10)

The One With Princess Consuela - S10-E14
Continuity mistake: When Rachel starts to cry, after Ross brings the champagne, Ross hugs her and holds the glass in his left hand, but when it cuts to the wideshot, the glass is instantly on the table in front of him. (00:10:20)
The One With The Secret Closet - S8-E14
Continuity mistake: In the scene where Rachel comes in to have Joey feel her stomach, he gets up from the bed and you can see the boxer shorts he is wearing. You can also see them at the end of the scene, even though he is supposed to be naked. (00:03:00)

The One With Phoebe's Dad - S2-E9
Continuity mistake: In the scene where Monica and Ross walk in carrying a few carrier bags, Monica takes out a pack of green plates, but in the next shot she is holding 4 packs of plates - 2 green, 2 red. She did not have time to pick up another pack between shots. (00:08:05)
The One With Rachel's Big Kiss - S7-E20
Continuity mistake: When Melissa and Rachel are first reunited at the Central Perk, the way they hold their arms (crossed, hands on hips, etc.) changes with almost every shot. (00:00:45)

The One with the Sonogram at the End - S1-E2
Continuity mistake: At the start of the episode when Chandler is talking about Pink Floyd, his legs are both on the table. When the shot changes, his right leg is resting on his left knee. (00:00:50)
The One With The Stripper - S8-E8
Continuity mistake: When Phoebe is trying to place the stripper at the beginning, her coffee cup on the table keeps changing position. (00:00:50)

The One Where Chandler Takes a Bath - S8-E13
Continuity mistake: When Joey is talking to Chandler about London, Chandler's wedding ring keeps disappearing and reappearing. (00:03:10)
Answer: The statements that she's contradicting (that it is common, it happens to every guy, and it's not a big deal), are the things that a woman commonly says to a man who is suffering from erectile difficulty, typically to assuage his bruised ego. However, most men do not believe that these statements are true, as evidenced by Chandler's outburst. He's so caught up in the proof that women are lying about it that he gives himself away.
Rooster of Doom