Did you replace the ends of the umbilical in an effort to resolve this issue, or is it something new?
Does the fuse blow if you wiggle, pull twist, push or bend the umbilical?
You might try replacing the fuse and then climb up with a ladder and smack your open palm against the side around each light. If the fuse blows gently pull that light fixture off and inspect for a wiring issue. If no issues found then with the fixture hanging go replace the fuse. Then go up the ladder and move the wires around to see if you can determine which wire is shorting.
If this issue is post cord end replacement you're going to have to open the ends up and find the short.
