Mine was doing this too, especially with the Boost switch on. Try adjusting the BBD Bias trimpot again, this time with a stronger input signal:
BBD Bias trim pot - Similar to the pot on a CE-2 or Caesar - Adjust for the least amount of distortion on the Wet signal, it's pretty obvious when set correctly: Set the Depth & Mix to 100% and turn up the output loud enough to clearly hear the signal. Start with trimpot set in the middle and very slightly turn up or down to hear where distortion starts, set it where there is the least distortion & noise. There is a range on the trimmer where you will hear the chorus effect. At either end of the range, there is quite a bit of fizz or distortion. Just set the trimmer for the least noise & best sound quality.
Here is the trimpot setup for the Gate trimpot as well:
GATE trim pot - User preference, it controls the frequency of the low pass filter portion of the gate. Start trimpot exactly halfway and try it with external Gate knob at 0%, 50%, & 100%. You want to have a range of options from very filtered at the lowest setting, to totally clean at the highest. - “I did have to fiddle with the external Gate pot on mine to get a setting where I could hear the chorusing clearly…you may have to play around a little to get it completely tuned in”
GATE trim from Shallow Water Manual:
"LPG ADJUST (i.e., GATE TRIM) - The recovery filter’s lowest frequency can be adjusted, to fine tune the way it will react to incoming signals. Lowering this frequency emphasizes the action of the low pass filter, effectively raising the threshold of sensitivity. Adjustment should be made with the following settings: MIX full wet, LPG minimum, DEPTH minimum. While listening to a signal going through the pedal, you’ll hear the effect of the recovery filter at its resting state. Carefully turn the trimpot labelled LPG adjust (i.e., GATE TRIM), clockwise to raise the filter’s frequency, counter-clockwise to lower. Be very careful, adjustments should be minimal as the trimpot is very sensitive. After each adjustment, LPG should be turned up momentarily to listen at the envelope’s response to the incoming signal."
