While the video was on YouTube Penny's voice was never heard asking if this always happens.
While chatting to Sheldon , Penny opens the top right-hand mailbox to get her mail.In later episodes her mailbox has moved 2 places to the left and is now next to Sheldon and Leonard's.
When Leonard and Penny go through his closet, they set some shirts on the bed. The shirts change position between shots.
The sign at the Topical Conference on Bose-Einstein Condensates introduces Leonard's research paper as "Paradoxical Movement-of-Inertia Changes Due to Putative Super-Solids", instead of "Moment-of-Inertia". The next scene includes a PowerPoint slide with the correct spelling.
In the first scene, when Howard is controlling things using his computer, for both turning on the light and turning down the stereo, it takes a few moments to work as the signal goes around the world, a trip that Howard reads out. However, turning on the stereo happens almost instantaneously, with no delay. This is inconsistent with the system they've set up.
The supersolid was discovered about 30 years before this aired.
While viewing the YouTube video, the browser had no URL in the address bar.
There is no error in the video that Leonard and Sheldon watch. There is obviously an edit that skips over the part where Penny speaks.