Electrical problem

So I learned a new skill last night. I changed my GFI under the sink of course the first time I didn't get everything tight enough and a black wire popped off. When I plugged in the camper I heard a loud pop and thought I had ruined it. I unplugged and looked at it and then was successful the second time. I did have one other problem and that was the little LED light on the extension cord. It would allow electric for a short time and then pop the circuit. I could see the light sparking when I plugged it in. I removed it and had power all night. The beep was low power to the propane detector. Thank you for all your help.