DDJ SX2 Deck 3 and 4 Playbutton

Hello.

I have a little problem and hope for help. Since yesterday I own a DDJ SX2. I'm also very happy with it, just a lot of me, that on deck 3 and 4 something is wrong.
When I switched to Decks 3 and 4, the play button did not blink anymore.
When I pressed Play there, nothing happened.

After a bit of rum, I found out that I have to press Shift-Play to start the deck. This is only true for Decks 3 and 4. Deck 1 and 2 work normally.

Did I overlook something in the console setting? Is that normal? If so, for what reason? Or is this simply a mistake and I would have to send in the device?

Thank you in advance for the help