The Higgs Boson Observation - S6-E3
Continuity mistake: At the end, when Alex and Sheldon are at the apartment, when Alex says "she seems nice", there are two beer bottles on the coffee table. The camera goes to Sheldon, and when it returns to Alex, there is only one bottle.
The Higgs Boson Observation - S6-E3
Factual error: Sheldon tells Alex that he's run a background check, including her medical records. There is no way he could obtain medical records without a HIPAA authorization signed by Alex herself. It's illegal.
The Higgs Boson Observation - S6-E3
Other mistake: Just before Amy video chats Sheldon there is a shot where she is wearing glasses, and when the camera zooms out she isn't.
The Higgs Boson Observation - S6-E3
Continuity mistake: Sheldon is taking composition books out of a box that was sent to him. When he first starts pulling them out, he has two composition book in one hand. Two shots later, he has only one composition book in his hand, but he is picking up a second one.
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.