The One With The Nap Partners - S7-E6
Continuity mistake: Monica and Chandler are in their apartment talking about Monica's worries that Chandler would dump her if she put on weight. When we first see Monica, the bite mark in her apple is quite small, but a few seconds later, it is suddenly much bigger without her eating any more of it. (00:18:00)
The One With The Nap Partners - S7-E6
Continuity mistake: When Ross and Joey wake from their nap on the couch while everyone else is watching them, Marvin the Martian stuffed doll is lying on the floor between the couch and wall, but in the closeups Marvin the Martian is on the couch.
The One With The Nap Partners - S7-E6
Continuity mistake: In the Maid Of Honour sequence, Joey's head starts to move one way. The camera cuts and it's no longer moving. (00:14:00)
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