Thanks for the excellent response. If it is hardware induced, is it possible to retrieve data from the phone? I would like to sell the phone, but don't want my data to fall into the wrong hands (for some reason there seems to a brisk market for hardbricked phones on Ebay). The phone had a pattern lock, but was not encrypted. It also had AHRD 91.1 and a 2.6 version of Twrp. I am 99% sure it is the motherboard since it randomly powered off and got very warm about 4 times before it completely died even after I performed recovery and clean flashes. Thanks again!