Electrical or ground issue?

Well, it sounds like an intermittent connection that is improved by heat. Usually it's the other way around. Any time you have a high amp condition, like ya'll did with the choke/ballast, the female connectors can lose their tension on the male side. I'd go back and remove the female connectors from the bulkhead and inspect thoroughly. You said it fried up to the bulkhead. It likely did not stop there.