Ikea Washbasin - Overflow Problems!

By the way, there's a video on the installation and even better systems from Ikea.

Thanks to you all, I've also seen the video. But which better systems do you mean ?
And yes , he also used the instructions. The problem was that for the thickness of the washbasin wall, the thread of the ring (silver part) was too short when you also put the seal on.
By the way, you can forget Ikea customer service. They offered me the siphon for kitchen sinks as an alternative.

Hadn't reported at all what the actual problem was. It was a manufacturing defect. Ikea would have taken back the sink. However, I would have had to dismantle it again for that.