Overflow Domsjö double sink IKEA, questions about overflow

Hi, unpleasant surprise when testing the overflow of the new domsjö sink: water escapes from the overflow at the bottom left and right on the sides and the mounting brackets. The two holes at the end of the overflow, i.e. in the area of the drain, also have side openings through which the water apparently continues to flow in the "ceramic belly" of the Domsjö. Who has the appropriate explanation? Many thanks in advance.

I will try to explain.

The sink is like a ceramic hand washbasin, a double-walled body with a hollow space.
Through the top opening, the overflow water flows into the entire hollow space, and through the lower holes of the drain cup into it.
The drain cup has special holes or recesses for this purpose.

The holes for the lower attachment of the basin are sealed with the gaskets included with the screw fittings, so that no water can leak out here.
This is only constructed this way for these sinks, but it will probably work.
I have not seen anything comparable in my practice, but you learn as you go.

I myself have not installed such a sink yet, but the installation instructions together with generally common practice actually say it all.
An overflow test should only be carried out on a fully installed sink.

This is written by a 64-year-old old hand with 50 years of construction experience.

Hello,
thank you very much for the explanation.

The problem is this:
no water from the two overflows of the double sink must under any circumstances enter the belly of the Domsjö. Especially since the belly is not sealed.
In the meantime, we have had the installation specialists here four or five times with four or five Domsjö sinks and always the same error. Absurd.
The overflow should correctly be a closed "tube" that only allows water to flow into the siphon. With all the Domsjös available to me so far, there were holes in the ceramic on the left and right at the end of the overflow in the area of the siphon. I suspect that water can/could flow into the Domsjö belly via this route and uncontrollably out through the four holes in the belly. No one at Ikea can or wants to explain what is happening there. It could quite well be that self-installers have not yet tested their Domsjö overflow and are not aware of the problem so far. Ikea might then have something else to deal with. Or was it just a faulty cast batch that was delivered in a locally limited area?

In any case, very annoying, especially since the model change is currently being carried out. We would not have bought this Ikea kitchen, as the porcelain sink was a decisive reason for us.