The old IDC problem... Hmm... 
Yes, the IDC connectors are not quite up to the job are they... 
Apparently, Williams needed to save costs and cut corners (save time).. DE did the same thing. IDC are not really rated for high current Pinball applications.
Yep, it is much quicker and cheaper to make wiring looms using IDC connectors, but as shown by wingtipvortex, they can be a problem...
