Like the rest of this review… this is just my opinion and what I think happened. The deck could have been a dud too, I haven’t had any issues with my 2nd build deck.
During my education, I’ve learned a fair bit about material strengths (just stuff that an airplane mechanic needs), but I would not call myself a metal specialist at all.
I haven’t seen any signs of arching or seen any reasons why 2 coils would really heat up the build deck so much that the wire sliced through as if it were butter. I would also not like to encourage others to try and replicate this issue… it’s too nice of an RDA to waste for a test