X600 sleep/power saving mode on AUX-in


I just received a new X600. It is working perfectly BUT if the AUX-in input is silent for 7-8 seconds then the unit enter some kind of sleep / energy saving mode and wakes up again when the music starts again. The problem is every time the music restarts, the X600 misses the first second of music.

Bluetooth on the x600 is fine.

I also own a Motion+ and the AUX-in is working just fine.

Any ideas to solve the problem? Thank you.