The One Where Chandler Crosses The Line - S4-E7
Continuity mistake: When Phoebe tells Ross that she wants to hear his "sound", she has her guitar in her lap. The shot changes, she says "Play that funky music white boy," and her guitar is missing. In the next shot, Ross runs out and her guitar is back on her lap again. (00:03:50)
The One Where Chandler Crosses The Line - S4-E7
Continuity mistake: When Chandler is showing Joey all of the new stuff in the apartment, the cuff on his right sleeve keeps going from messy to neat between shots. (00:13:45)
The One Where Chandler Crosses The Line - S4-E7
Continuity mistake: When Ross and Phoebe are talking in Central Perk, Phoebe's position changes. (00:14:45)
The One Where Chandler Crosses The Line - S4-E7
Continuity mistake: When Cathy and Chandler are talking while sitting inside the boat, the silver object on the corner of the counter behind Chandler disappears between shots. (00:08:20)
The One Where Chandler Crosses The Line - S4-E7
Continuity mistake: When Ross is telling Monica and Phoebe that he found his "sound" in college, Monica spits out her orange juice and places the glass on the coffee table. The shot changes to Phoebe and you can see Monica putting the glass down again. (00:03:30)
The One Where Chandler Crosses The Line - S4-E7
Continuity mistake: In the final scene wherein Phoebe finally agrees to play guitar again, Ross moves from the armchair to the sofa. As he sits down, his arm is by his side, but when the camera angle shifts, it is on the back of the sofa. (00:20:50)
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