The Convention Conundrum - S7-E14
Character mistake: On Sheldon's board of possible attendees for his convention he has misspelled Ian McKellen - with 'an' at the end.
The Discovery Dissipation - S7-E10
Continuity mistake: The Stevenson Award in Sheldon's office reads "Sheldon Cooper, PhD." But, in the "Dennis Kim" episode we are told Sheldon was 14.5 years old when he earned that award - 1.5 years before earning his PhD at age 16, so the award should not show the title of PhD.
The Mommy Observation - S7-E18
Factual error: Based on the length of Bernadette's skirt and the place she's standing, Stuart could never see under it.
The Cooper Extraction - S7-E11
Continuity mistake: When Amy says that Penny never would have met Stan Lee, she draws a thick black line between "Penny" and "Stan Lee" on the board. The camera goes to Penny, and when it comes back to Amy, the line is blue and faint.
The Proton Displacement - S7-E7
Continuity mistake: During the jewelry-making session, when Penny is making a mess, there's a black piece stuck to her left hand. The piece is stuck on different parts of her hand throughout the scene. (00:07:15)
The Deception Verification - S7-E2
Continuity mistake: In the scene where Howard and Raj are comparing the size of their breast area, Bernadette is seen in the background holding a mug with the handle in her right hand. However, when the scene zooms in on her, the handle appears in her left hand.
The Gorilla Dissolution - S7-E23
Revealing mistake: After Howard lets go of the unpacked treadmill, it begins to fall down the stairs. As it goes out of frame, the treadmill begins to level itself out, but the sound of it is still heard falling and Howard, Bernadette and Raj continue running past, way further than where it levelled itself out anyway. (00:00:35)
The Thanksgiving Decoupling - S7-E9
Continuity mistake: When Sheldon and Mike are drunk on the couch after Howard leaves, they are toasting with the beer cans. Sheldon has his in his right hand, but when Bernardette came in, the can is in his left. A little bit later, after he says "she's so tiny", the can moves back to his right hand.
The Locomotive Manipulation - S7-E15
Continuity mistake: At the end of the episode when Lennard asks Sheldon about his train ride, he says that he kissed Amy on the lips, and says that it tasted like the brownies that they had that for dessert. But they were eating a tart of some type, with a shortbread crust. No brownies were on the table.
The Discovery Dissipation - S7-E10
Continuity mistake: In Season 3 Episode 1 Sheldon made a retraction of his paper. But here he says he had only one retraction, when he was a kid. (00:11:36 - 00:13:09)
The Proton Displacement - S7-E7
Character mistake: When Raj shows Penny, Amy, and Bernadette how to make jewelry, Penny keeps having trouble with the glue and gets it all over her fingers. However, in Season 2, episode 5, she has no trouble at all with the glue when making 1000 Penny Blossoms.
Answer: Because Raj's selective mutism seems to be caused by women that Raj sees (on some sort of conscious or subconscious level) as a potential sexual partner. An attribute that wouldn't apply to either his sister or mother.