If anyone is having issues with the headset floating, then either your setup is off, your playing environment is off, or something is blocking the headset during gameplay. The chances of having a "broken" headset are extremely low.
Tino, do you play seated? If so, try playing at the front edge of the seat, or leaning forward a bit so that your head is not near or against the back / headrest of the seat. I'm curious about something. If you don't play this way, then disregard.