Originally Posted by MadMorbius
Weird, the damage will usually happen at the short location. I don't think you pinched a wire, I think your plug was defective, possibly missing the plastic insulation between the positive/negative leads. The damage on the plug suggest arcing in that area.
Replacing the connection with a Deans plug might address the short, if nothing else was fried in the process.
From my experience as an apprentice electrician, and just saying from what i've learned is(and i'm not saying i'm an expert or know everything); that if it has been done in this order, while screwing in the plate he pinched the wire and AFTER plugged in the battery, the location of the short would be at the connection of the battery and not where the wire was snagged.
But in his case as he explained, he plugged it in, started screwing in the butt plate and smoke started appearing, so it had to be arcing at the connector (look at his pics)
Even I find it odd..