Factory reset, cache/data wipe did not work. So unlocked bootloader to be able to flash factory images and no build/version of 4.3 or 4.4 worked. 4.2 works but boot time is an abnormal 100+ seconds, but otherwise is fine. If however I update from 4.2 to 4.3, it goes back to bootlooping.
Its almost as if the phone is now suddenly incompatible with 4.3 and 4.4.
I read all relevant threads online on XDA and elsewhere and this doesn't seem like those issues. The sensors are all functioning and there are no loose cables since I used a sensor app and all sensors are giving readings (including proximity). Also tried to downgrade radio version from .84 (of 4.3 and above) to .48 (of 4.2) to see if it makes it work it did not. Then I tried upgrading the radio of a working 4.2 install from .48 to .84 and that din't break it. So radio version is not the issue here either.