It seems like you would need a sustained short in order to dump energy into the inductor during the current pulse. Then when the high current clears the short, the inductor delivers the high voltage to cause the sparking.
There was some sparking for a while just before the current increased. I captured one event and will post images in a bit. On release of the short 21 volts was observed at the electrodes. Now that the cell is boiling, those events seem to have stopped.