[Al Skierkiewicz]

For all,
Once the FETs have become comprimised it is possible for them to spark for a while before total destruction. The initial damage will blow the case open showering molten semiconductor inside the case. The sparks are always accompanied by a really bad burning smell. It is a smell you will never forget, the death throes of a power FET and it's melting case.
This is not a survivable event, replace the controller.