Rimless toilet overflows sideways when flushing - any ideas?

Hi everyone,
we have installed the Ideal Standard Connect wall-mounted siphonic toilet with "Aquablade" in the house. Identical in the bathroom and the WC.
While everything works perfectly in the bathroom, we have the problem in the WC that a lot of water runs out sideways during flushing. I have attached some pictures.
Now we can be fairly sure that it is not due to the design (we have two and one of them is okay). Nevertheless, we of course wonder whether it is a Monday toilet, or if we can do something ourselves to fix it.
It is rimless and only has a small slit there. I once ran a very fine brush along the rear edge. After that, it felt better for a while and I thought the issue was fixed. But recently it started again. It’s not just a little bit, but a lot of water running out sideways. Has anyone experienced a similar problem? How can it be solved? Could it be that something is stuck under the narrow flushing slit due to manufacturing reasons and the water therefore does not flow correctly?

Flush pipe inserted too far into the toilet or too much pressure due to too much water. There are such brakes... more than 6 liters usually do not work

Is it perhaps not hanging completely straight?

That looks just like a whirlpool :D

When we got a rimless toilet, the installer said we should get in touch if anything leaks. Then he could adjust the amount of water during the flush. So maybe too much water is coming out for you, or it’s not hanging straight, or whatever... I would contact the installer, they can probably fix it. Especially if there’s no problem with the same model in the other bathroom.

A little update on this: An attempt was made to adjust the amount of rinse water in this box, but that did not bring any lasting improvement. We contacted the manufacturer, who sent us a kind of plastic perforated disk without any comment. I assume that is supposed to reduce the water pressure a bit? Now we just need to get the installer back to fix it. They are all always extremely busy, and by now we have kind of fallen off the radar because we are considered "finished."