The Secret Box / Band Geeks - S2-E14
Audio problem: At the end of "Band Geeks" when everyone is playing "Sweet Victory" at one point Mrs. Puff is shown playing the guitar. When this happens, you can see the others in the background not doing anything, even though their instruments are heard.
You Wish ('Shanghaied') / Gary Takes A Bath - S2-E11
Audio problem: In the beginning of "Shanghaied" during the Patchy the Pirate segment, Patchy says, "Roll the cartoon" but his mouth obviously says something else.
Pressure / The Smoking Peanut - S2-E12
Audio problem: In the beginning of "The Smoking Peanut", Spongebob takes his hat and spits it in the air like Clamu would do. Before he puts the hat in his mouth, he says, "a cannonball", the camera is on Spongebob and his mouth isn't saying that. He has his mouth open to put the hat in his mouth.
Grandma's Kisses / Squidville - S2-E9
Audio problem: After SpongeBob causes a flood in his grandma's house, he cries because he is fed up of being an adult and his grandma tells him he doesn't have to be a baby to get her love. When SpongeBob replies, "I'm not?" note that in his reflection, his mouth does not move.
Your Shoe's Untied / Squid's Day Off - S2-E2
Audio problem: In "Your Shoe's Untied" when Gary ties Spongebob's shoes he says "hoppin' clams where'd you learn to do that?" When he says "clams" his lips are out of sync.
Mermaid Man and Barnacle Boy III / Squirrel Jokes - S2-E4
Audio problem: In "Squirrel Jokes" when Sandy is in the Bargn'-Mart and she can't decide which deodorant she wants, a fish says, "Maybe she should get both." His mouth says something else.
The Bully / Just One Bite - S2-E17
Audio problem: In "Just One Bite", Squidward is running, then tiptoeing by Spongebob's house. The sound of his running is fine, but the sound of tiptoeing is faster and not in sync with with movement.
Answer: I believe this is the Season 6 episode "Spongicus".