Could you please help me understand a wiring issue I'm having? I have #12 hot and neutral running from a new 20amp GE breaker through 1/2" EMT to a junction box. From the JB I have 12/2 metal clad (Armorlite with aluminum sheathing) running behind drywall (old work) to a 15amp receptacle in a metal box. If I connect the ground in the junction box to the ground screw on the receptacle, the breaker trips. If I simply cap off the ground, I have no problems. I thought you are supposed to always ground metal clad to the junction box and outlet. It seems like the metal clad sheath is acting as the ground. Thank you in advance for your thoughts and assistance!