The OP needs to attend a "Converters Anonymous" meeting. Kind of in denial that he has a problem. Anytime you have lights that are dimming or a surge in 12V power, it can be assumed that the power supply in the converter has gone South. The real bad thing about the WFCO converters is that the output regulation circuit is also poorly implemented. Who knows what type of current and voltage will be pushed at the batteries and at various circuit boards?
I'd suggest to change out the WFCO converter, yesterday.