50A pigtail rewire

[doc4]

Each time I plugin ground power I trip ground's GFI. My 50A pigtail has "broken" loose from the rubber that surrounds it and cable. I thought I'd start there since the head is very floppy and probably has broken wires. How are the wires (White, green, black and red) mated to a replacement (such as found @ camp stores and Camping World)? Suggestions? Thx.... Doc4.

[jpf]

black and red are hot and go to each arm.
green is ground and goes to top U.
white is neutral and goes to bottom.