Has this always happened, or is it a new problem..? If, so, what has changed since it last worked well..? With any active bass or guitar, in case of problems, the very first thing to do is to change the batteries for new ones. It might help, or it might not, but it at least eliminates any doubt, and gives a firm basis for further investigation, if needed. Nine times out of ten, it cures the problem, though, so do that first, I'd say.