I've followed these instructions and sadly this has now left my phone not booting up with both the old battery (which was working fine previously) and the brand new replacement OEM battery. :( All it does is flash the red LED when I attempt to turn it on and I've left it to charge overnight and it remains to treat both batteries continually as if they're always empty. :( Anyone get any advice on this issue, or is this just a risk of replacing a Sony Xperia Z2 battery? :(