The One After the Superbowl, part 2 - S2-E13
Continuity mistake: Chandler is talking to Susie (Julia Roberts) and a man is standing behind Chandler in a doorway. There is a cut to Susie, but when the camera goes back to Chandler the man is not there. Then he appears again. (00:03:20)
The One After the Superbowl, part 2 - S2-E13
Continuity mistake: In the coffee house, while Chandler is talking about his date with Susie, a tall man with a blue shirt and vest gets up and walks toward the door twice. (00:07:30)
The One After the Superbowl, part 2 - S2-E13
Continuity mistake: When Susie is asking Chandler to wear her undies, her hand is on his neck. In the next shot it is gone, and then it is back again. (00:08:45)
The One After the Superbowl, part 2 - S2-E13
Continuity mistake: When Chandler removes his clothes while he and Susie are in the bathroom, Susie picks up both of his shoes and holds them in her arms in all of her closeups, but when Chandler's standing on the toilet one of his shoes is still on the floor in the wideshots.
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