done that, but its still possible somewhere im sure. use a meter, its showing 12.8 volts at panel, using black wire at ground, so I believe its good to this point.If you haven’t already, find and clean any and all grounding points.
Not just at the battery but at the engine. Trace the negative cable and clean and tighten all connection points. These bolts get corroded or loose and cause all sorts of strange problems.
ive called in reinforcements ( a real mechanic) before i buy a control panel.