One other question, does the “spitting/arcing” occur without music playing? If so, this could be caused by dust or particulates trapped between the stator and membrane, it can also manifest itself in form of whistling, buzzing. Generally, this resolves itself on its own. I have experienced this with earlier panel versions although, so far, not with my current Bass Focus 845PX’s.
Another thought, does the music your currently playing contain greater bass energy than that played in the past? If that is the case you might have reached the panels output limits.
Anyhow, I’m only throwing out a few ideas. There may actually be an issue with the panels. That said, the PX panels, as I’m sure Tom will agree, have been the most
reliable of any produced in Soundlab’s history.