Cold Weather Wiper Defroster Causing Burning?

I recently noticed a strong burning smell and noticed a smoking/yellowish substance on my passenger side windshield right under approximately the center of the wiper blade. I got out to inspect it and didnt notice anything unusual and under the hood, everything checked out and there was no burning smells so I drove home. almost a week later, I was driving and noticed the smell again, this time though I heard a crack and immediately saw a split in my windshield. This time when I got out to look, there was distinct bubbling from heat, cracking and discoloration from a burn in the black portion in the same location. I have a 2012 Rock Warrior edition with the cold weather and tow package and I understand that it comes with defrosters under the wiper blasdes... so my best guess at this point its that it overheated and casued the burning and windshield to crack.... however I am not 100% sure that this is what happaned, plus even if it was... what was the underlying cause? a short? Will replacing the winshield fix it, or will I install a new windshield only to have it crack again?

 

I think there was something wrong with the windshield causing a hot spot like that. Something wrong with the defroster element.

 

Sounds familiar with the 4runners rear hatch glasses shattering from the defroster.