make sure your Firmware of the SR is 1.08
Check the Manual on Page 26-27
Switch to Utility Mode
Setting the Master Output´s Attenuation level
set it to [HOT CUE] should work well
Turn off the device and Try again.
Also check the settings in serato (auto gain is set to +92 dB)*this is my preference*
can you also test the Booth output on the device!?