Audio problem: As Carlos is giving his speech at the barbecue, Julie sees Zach and says to Susan "Oh God". After cutting to a shot of Zach and his father it shows Julie and Susan again. If you look to the right of the shot you will see Carlos' face is just looking in front of him and not speaking, but you can still hear him giving his speech whilst he is in shot.
Audio problem: When Susan suspects someone might be in the house, the seduction music she has put on for Mike is drowned out by the score. When she accidentally hits Mike across the face, the score stops, but the music that was playing in the background has gone. The song in the background before now was music within the show, and it was loud enough to be heard around the house, so we should still be able to hear it.
Audio problem: When Eva Longorea drives home her husband is talking to a man. Their lips move, but no sound comes out.
Your Fault - S1-E13
Audio problem: At the school dance, the students are all dancing at a rapid pace when the music playing is a slow song, indicative that the music was dubbed in later.
Audio problem: When Gaby goes to introduce Angie to Heidi Klum at the fashion agency, Gaby goes up to Heidi and says "It's me, Gaby." When the camera angle changes to behind Gaby in the next shot, she is saying the same thing again, but no words are coming out.
Sweetheart, I Have to Confess - S3-E6
Audio problem: Right after Nora kisses Tom when she says "hey, lets have some more wine.", her lips don't match the words.
Audio problem: When Gaby's charity modelling event takes place and Susan, after being roughed up by John Rolland's mother after mistakenly accusing her of sleeping with her son, Tom starts talking but you can see him in the left corner of the scene without his mouth moving at all.
Audio problem: When the Stagehand says "Come on, you're up!" to Susan before she is about to go on the catwalk at Gabrielle's fashion show, the words do not match his lips.
Audio problem: During the dinner scene at the Scavo's home, Lynette tells Irina that her son Preston is "blinded by a piece of Eurotrash who would sell her own mother for a pair of designer jeans." When the camera changes to behind Lynette in the next shot, she can be saying the words "designer jeans" again, but this time with no sound.
Audio problem: When Lynette warns Anne to never lay a finger on her son Porter again, from behind Lynette's head she is still talking, but no words are coming out.
Audio problem: When Lynette slaps Anne Schilling across the face in the wash room, a slapping sound can be heard after her hand goes past Anne's face.
Audio problem: When Susan is on the catwalk at Gabrielle's fashion show, Tom announces what she is wearing, but if you look in the background you can see his lips are not moving when he is speaking.
Audio problem: When Lynette tells her sons to clean their teeth in the bathroom, the boys turn around and in the mirror you can see Lynette saying the same thing with no sound.
Audio problem: The opera singer seen at the beginning at the episode is dubbed. His lip movements don't quite match the tune.
Audio problem: Season 2, Episode 17: "Could I Leave You?" - Veronica's son's lip movements do not match when he tells her that he's thirsty.
Audio problem: When Gaby sees Paulina Poriskova in the restaurant, she puts out her arms and says, "Give me a hug!" but her lips barely move.
Answer: Kayla was sent away in episode 16 (The Gun Song) in season 4, after falsely accusing Lynette of child abuse. She now lives with her grandparents - probably Nora's parents.
I'm curious why we never see her again, why she never talked about, and why Tom never mentions visiting her.