The One With The Ultimate Fighting Champion - S3-E24
Continuity mistake: After Rachel and Phoebe see Bonnie and Ross in Central Perk, Rachel is yelling at Phoebe that she needs to break them up. At first, Phoebe is holding her coat in her left hand and a purse in her right, but then she is holding them both in her left, with no time to have changed hands. (00:16:30)
The One With The Ultimate Fighting Champion - S3-E24
Continuity mistake: When Chandler's boss is slapping all the guys on the butt, on the side of the table closest to the camera there is a tablet with a pen on it. When the guy comes back in to get his briefcase, the pen is no longer there. (00:20:35)
The One With The Ultimate Fighting Champion - S3-E24
Continuity mistake: In the scene with Robin Williams and Billy Crystal, there is a shot of Rachel, and her hair is hanging straight down. The next shot of Rachel is from a different angle and there is a section of hair behind her ear; in the shot after that it is hanging straight again, and is then behind her ears again. (00:00:40)
The One With The Ultimate Fighting Champion - S3-E24
Continuity mistake: When Robin Williams calls Billy Crystal a b*stard, Monica's purse goes from on her lap to being on her shoulder. (00:01:30)
The One With The Ultimate Fighting Champion - S3-E24
Continuity mistake: Joey's hair is suddenly much shorter after the intro with Robin Williams and Billy Crystal - everyone's wearing the same clothes so no time is meant to have passed.
The One With The Ultimate Fighting Champion - S3-E24
Continuity mistake: Ross buys the Ultimate Fighting Combo, a large pop and popcorn at the fight, but when he and Monica sit down, they are never seen again. Furthermore, when Monica talks to Pete at the ring, you can see that the Combo was not set on the floor.
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