Watch out for Black on Black/ Red on Red circuit 'crossovers'.
I can' speak to the residential situation but many's the time that my apprentices cross circuit 1 with circuit 7 in a three phase system.
Naturally, this permits the wire to draw across double breakers -- completely defeating their protection: #12 is now able to receive 40 continous amperes!
Could anything like that have happened to you?
This kind of circuit fault is just another reason why deliberately faulting circuits is so risky, especially troubled circuits.
