bandpass filter leaving trail of clicks

Hi,

I am experiencing something strange with the filtergraph~/biquad~ combo. When the filter is set to bandpass and is in a certain range, it emits a subtle trail of (relatively bassy) clicks once the filtered sound is finished playing. Sometimes this goes on for a long time, other times not so long. Sometimes it's louder than other times; all this based on exactly where the cutoff is set. Does anyone know what might be causing this noise and how I may go about getting rid of it?

Thanks in advance,
Jay