Jim W mentioned there has been an intermittant ~20 Hz noise source observed by the HAM5 GS13s (he mentioned it being seen on the SRM OSEMs as well).  Attachment #1 shows channels for Y & RX BLRMS for 10-30Hz where there are times when the noise appears.  

Attachment #2 is a screenshot of nuc6 with the new temporary StripTool for HAM5 ISI.  If the channels here stray from 0, then there could be an issue with the SRM/HAM5ISI.