I noticed that radiation instrumentation readings are frozen. Water temperature has also remained to 108.1 °C for a while.
The labjack USB connection shut down, so the data stopped updating. Another detail to fix, but the audio and power monitoring worked OK.
Regarding the resonant noise, it was clearly related to a series of short (100 usec) discharge events as shown on the scope. There was also some fireworks visible on the camera image of the cell, though dimmed by the nearly-opaque electrolyte.