DDJ-SB2 : Getting very low headphone volume

I'm using DDJ SB2 and serato dj intro. When I start the software initially I get a good headphone volume level but after some seconds the limiter gets on and the headphone volume is decreased and if I decrease the level of trim knob to 50% then the limiter gets off but still the headphone volume is very low. The headphone level knob is full and cue switches are also on but I cant even hear anything.