Hello, after I upgraded to Nougat using the 7.2.9 build, now I cannot flash any new updates. I tried to unlock the bootloader using the unlock tool. It succeeded, but on subsequent upgrade retries the phone reboots with the same old 7.2.9 version. If I try the unlock tool again, it says it is not necessary to unlock (already unlocked?), but I still cannot upgrade. The current version (7.2.9) heats horribly and depletes the batteries in half a day. Any ideas what else can I do?