The Barbarian Sublimation - S2-E3
Continuity mistake: At the start, after Penny has dropped one bag, there is an item in the top of the remaining bag. This item keeps appearing and disappearing. (00:01:20)
The Barbarian Sublimation - S2-E3
Continuity mistake: After Penny drops her bags of groceries whilst trying to unlock her door, the dropped items change their positions between shots (note the items against the wall.) (00:02:05)
The Barbarian Sublimation - S2-E3
Continuity mistake: When Penny explains she has bought the game, her grip on the laptop changes. (00:06:50)
The Barbarian Sublimation - S2-E3
Continuity mistake: When Penny sneaks into Sheldon's room at night to ask him about the online game, she leaves his bedroom door half open. But when she leaves, the door is shut. (00:07:35)
The Barbarian Sublimation - S2-E3
Continuity mistake: When Leslie and Sheldon are talking to Dr. Eric Gablehauser in his office, in one shot Eric throws a piece of paper onto the desk behind him (next to the computer.) Through the rest of the scene, this piece of paper keeps changing position. (00:09:00)
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.