Hi,
I owned a DBS400 for 10 years, and it was mostly reliable.
It did develop a problem where the sound would cut in and out - tried leads, speaker connections, etc.
Solution: Input jacks are in the same signal path as the effects send/receive - if you have no effects plugged in then loop the effects send/return jacks with a cord. These jacks can go high resistance and cut your input signal.
Never had a problem after doing this.
Mike