[X 2014 Q&A, Help & Troubleshooting] egorikem:
Thanks for the response! However, my unit was purchased at Stapes (lol, I know) as a Unlocked version. I know, it is confusing for me as well. And yes, I have tried about 5 versions of firmware, none worked. I even made a little script to automate the process:

github.com/egorikem/Flash-Android

I was able to find a device with fastboot serial of TA9890DMWW

Any key to continue, or Ctrl+C to abort

Flashing partition...
target reported max download size of 536870912 bytes
sending 'partition' (32 KB)...
OKAY [ 0.003s]
writing 'partition'...
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 0.112s
Done
Flashing motoboot...
target reported max download size of 536870912 bytes
sending 'motoboot' (2022 KB)...
OKAY [ 0.116s]
writing 'motoboot'...
(bootloader) Motoboot: Preflash validation for tz
(bootloader) Preflash validation failed
FAILED (remote failure)
finished. total time: 0.217s
Done
Rebooting device...
rebooting into bootloader...
OKAY [ 0.001s]
finished. total time: 0.001s
Done
Flashing logo...
ERROR: Unable to create a plug-in (e00002be)
< waiting for device >
target reported max download size of 536870912 bytes
sending 'logo' (467 KB)...
OKAY [ 0.016s]
writing 'logo'...
OKAY [ 0.048s]
finished. total time: 0.065s
Done
Flashing boot...
target reported max download size of 536870912 bytes
sending 'boot' (10200 KB)...
OKAY [ 0.353s]
writing 'boot'...
OKAY [ 0.419s]
finished. total time: 0.773s
Done
Flashing recovery...
target reported max download size of 536870912 bytes
sending 'recovery' (10280 KB)...
OKAY [ 0.374s]
writing 'recovery'...
OKAY [ 0.426s]
finished. total time: 0.800s
Done
Flashing system...
target max-sparse-size: 256MB
sending 'system' (256598 KB)...
OKAY [ 8.110s]
writing 'system'...
OKAY [ 6.969s]
finished. total time: 15.078s
Done
target max-sparse-size: 256MB
sending 'system' (256089 KB)...
OKAY [ 8.103s]
writing 'system'...
OKAY [ 4.991s]
finished. total time: 13.094s
Done
target max-sparse-size: 256MB
sending 'system' (256726 KB)...
OKAY [ 8.099s]
writing 'system'...
OKAY [ 5.298s]
finished. total time: 13.397s
Done
target max-sparse-size: 256MB
sending 'system' (256695 KB)...
OKAY [ 8.114s]
writing 'system'...
OKAY [ 5.439s]
finished. total time: 13.553s
Done
target max-sparse-size: 256MB
sending 'system' (256177 KB)...
OKAY [ 8.096s]
writing 'system'...
OKAY [ 5.828s]
finished. total time: 13.924s
Done
target max-sparse-size: 256MB
sending 'system' (257618 KB)...
OKAY [ 8.155s]
writing 'system'...
OKAY [ 5.380s]
finished. total time: 13.536s
Done
target max-sparse-size: 256MB
sending 'system' (257940 KB)...
OKAY [ 8.157s]
writing 'system'...
OKAY [ 4.782s]
finished. total time: 12.939s
Done
target max-sparse-size: 256MB
sending 'system' (64164 KB)...
OKAY [ 2.063s]
writing 'system'...
OKAY [ 1.219s]
finished. total time: 3.283s
Done
target max-sparse-size: 256MB
error: cannot load './system.img_sparsechunk.8': No such file or directory

Done
Done
Erasing previous bands...
erasing 'modemst1'...
OKAY [ 0.052s]
finished. total time: 0.052s
erasing 'modemst2'...
OKAY [ 0.048s]
finished. total time: 0.048s
Done
target reported max download size of 536870912 bytes
sending 'fsg' (694 KB)...
OKAY [ 0.023s]
writing 'fsg'...
OKAY [ 0.040s]
finished. total time: 0.064s
Done
target reported max download size of 536870912 bytes
sending 'modem' (62248 KB)...
OKAY [ 2.038s]
writing 'modem'...
OKAY [ 1.229s]
finished. total time: 3.267s
Done
erasing 'userdata'...
OKAY [ 1.308s]
finished. total time: 1.308s
erasing 'cache'...
OKAY [ 0.305s]
finished. total time: 0.305s
Done
Rebooting device...
rebooting...

finished. total time: 0.001s
Done! Have fun, your device is ready