Hi oVerDriver. Due to the design of the single-belt mechanism of the CSL Elite bases, there is a small amount of play that results in some noise generation. The belt can end up being more or less tensioned (to a small degree) due to manufacturing tolerances. The amount of noise the base makes through normal operation is highly dependent on the game being used, the car, the car setup, the track, the track conditions, the in-game force feedback settings, and the Fanatec Tuning Menu settings. Lower DRI and FEI values help to reduce the sound. The surface or rig that the base is attached to can also amplify or reduce the sound.
"I think there may be something loose inside the base, feels a bit like belt teeth is moving between the gear teeth." - If this was the case, the effect would be be much more pronounced. I really doubt that is happening.
If the unit was assessed to be more noisy or a worse feel than expected, we would resolve this within warranty, but we can't do that based on a video alone. However my first impression is that your wheel appears to be normal.
I have to disagree there Krassi. The CSL Elite bases all exhibit some degree of mechanical 'knocking' that is inherent to the single belt design. Having some play contributes to the characteristic smoothness of the CSL steering, so there is a tradeoff.