4 Decks simultan Serato & Rekordbox did not work

Hello Pioneer Team
As a DJ I like to work with 4 decks (2 CDJ and 2 turntables). The DJM-S9 is a 2 deck mixer, but when I bought it I was informed that you can use 4 decks at the same time. But that doesn't seem to work - or is the German translation in the DJM-S9 manual wrong?

When switching from deck 1 to 3, the sound on deck 1 is switched off. The same on the other side. And that regardless if CDJ, Turntable, XDJ or nothing at all is connected. (Serato & rekordbox).

The manual says "simultaneous use" and this means that you can use ALL 4 decks and not only 2 decks at a time. But to connect the phono on deck 1+ 3 (probably one on CD Line & Phono) and the XDJ on deck 2+4 makes no sense, because then the turntable is on the left and the XDJ on the right. Nobody hangs up like that. The setting then says CH1 is Deck 1 + 3 and CH2 is for Deck 2 +4.

That can't be true, can it???

Thanks for your feedback and greetings from Switzerland

Translated with www.DeepL.com/Translator