Extract the files below from there respective fxz file and try the commands listed. You must use the updated moto-fastboot.exe app. I just have it renamed to fastboot.exe. files from 5.5.893 tar.gz file posted above (credit to realbbb): fastboot flash boot boot.img fastboot flash recovery recovery.img files from stock 5.5.866 fxz file: fastboot flash system system.img fastboot flash preinstall preinstall.img fastboot flash radio radio.img fastboot flash webtop grfs.img (might not be necessary, but I did it) Boot the phone into fastboot mode. I put all of the files in the same folder and flashed them one after the other. Then "fastboot reboot". I booted up fine and shortly thereafter had a notificaton of an available update. I then used R3L3AS3D to root and 4ever root and allowed the update. So far everything is working great and I'm on the OTA path again. All credit for this method goes to Timmy10shoes.
Did these steps..it got me from the AP FastBoot Boot Failure and finally got into Android...
Once booted up, I reboot and ran 4ever 2.1
Press any key to continue . . .
* Flashing system.img....This will take about 2-5 minutes
sending 'system' (491264 KB)... OKAY
writing 'system'... INFOPreflash validation failure
FAILED (remote: )
* Wiping data and cache
erasing 'userdata'... OKAY
erasing 'cache'... OKAY
* Rebooting your phone now, factory 886 system restored
* This will take a bit so be patient.
* Once your phone is rebooted we can start rooting it
Now I am back to square one again....
AP Fastboot Flash Mode S Flash Failure