[Someone1234]

I own the QC25's and I can say they work just fine without me having to install a piece of paper in the cup.

The video you linked to is a repair video, but your comment implies that a new set taken off the shelf don't work unless you install paper, two different things entirely.

I haven't yet had an issue with the QC25s except that they do seem to cause noise fatigue a lot quicker than non-noise cancelling headphones. I cannot explain that; just my experience. But the noise cancelling is very good.