Could you please help me understand a wiring issue I'm having? I have #12 hot and neutral running from a new GE 20amp breaker to a metal junction box. From the jb I have 12/2 armor clad running behind drywall (old work) to a metal box with a 15amp outlet. If I connect the copper (green) ground from the metal clad (which is aluminum corrugated sheathing) to the junction box on one end and to the receptacle ground screw on the other end, the breaker trips. If I simply cap off the ground on both sides, I have no problems. I thought you are supposed to always ground metal clad to the junction box and outlet. Is the aluminum clad acting as the ground? I have run circuits like this in the past and did ground the metal clad to the jb and the receptacle ground screw without an issue. What am I not understanding? Thank you!