Here you go!
Towelroot doesn't work anymore!
edit; modstring "1337 0 1 7380 4 0" also results in "Phone isn't currently supported"
obviously, that's because the kernel is build on 23/07/2014.
Have a look on the internet..
This is normal.
If you search this subject, you'll find a LOT of answers and things you can do.
I do not think that is a flashing problem , i think is related to gmail sync. delete your contacts and gmail account and create it again...it should solve it
Try to factory reset it , do not restore back up (yet) and see if is wo...