I cannot reproduce. Here are my steps would it be possible to revise them if incorrect?
Create new project in Sonar X3D.
Insert Battery soft synth.
Bring up Pro Channel Console
At the top of the channel (1) for the battery soft synth, observe gain set at zero.
Change gain knob to -17.
Drag a drum loop MIDI pattern into the track.
Press the loop button (so it turns blue) and set the marker points appropriately for a repetitive loop.
Turn on the metronome for playback.
Play for five minutes.