not my setup but have all the bits to get it working
skim through the older pages of the thread to find the origin of the photo
yeah mine was a bit intermittent, after constant use the heat in the cable may make the power drop as well .
pretty cheap fix for myself:
$8- ba ford starter cable from wreckers
$5/10 - battery lugs from jaycar
keep the factory cable there and just add another positive cable to terminal in the engine bay to see if its a fix, if not will have to get a 2nd hand cable from a r33 wreck, welding store for the use of welder ground cable which i'm told is priced ok or ebay