According to raito-kun, he says that U&I's concert is also Kigami's work:

https://aninomiyako.wordpress.com/2010/09/04/k-on-key-animation-books/

ritsu's flick at 0:05 confuses me somehow

untai said:
ritsu's flick at 0:05 confuses me somehow

It looks like the satsuei messed up the frames.
The drumsticks she has in cross at 0:05 where the weird flick happens is probably A1, inserted wrongly. It should be at the start of the cut, not towards the end. So the cut starts on A2, so to speak, and A1 is mistakenly placed in the middle.

Habarudo said:
It looks like the satsuei messed up the frames.
The drumsticks she has in cross at 0:05 where the weird flick happens is probably A1, inserted wrongly. It should be at the start of the cut, not towards the end. So the cut starts on A2, so to speak, and A1 is mistakenly placed in the middle.

yeah, i also thought it would be too weird if it was an animator's (the animator's!) mistake. thanks a lot