[Moto G Q&A, Help & Troubleshooting] campusantu:
Please note: I know there are other guides here on XDA but none worked for me, so I'm writing this to help other stuck people.

Disclaimer: I tested this on my XT1032, I don't know if or how it will work on other variants. Following this guide you'll lose all data on your phone, make sure to backup important stuff. I'm not responsible for what you do to your phone following this guide (anyway if you're here probably you have not much to lose...)

Introduction

What happened: a couple of weeks ago I wanted to try GPE rom on my XT1032, so I flashed the appropriate rom for my device (4.4.3 KOT49H.M004) and then applied OTA (4.4.3 KOT49H.M004 to 4.4.4 KTU84P.M003). Today I decided to go back to stock, so I rebooted in bootloader mode and tried to flash stock 4.4.3.

Result: a bunch of fastboot errors, ranging from "wrong size partitions", to "preflash validation failed", to ... well I don't remember all of them, as I said they were a lot..

Then I tried older versions, I tried to reflash 4.4.3 GPE, I tried to follow guides, here on XDA and around the vast internet.. All with no luck. Until I found one and, long story short I did it. I'm back to stock 4.4.4 (flashed stock 4.4.3 and applied OTA)

I'm sharing this what I did to recover from the soft-brick, hoping to help someone. This guide is not a temporary workaround while waiting for full 4.4.4 GPE image, this will fully restore your Moto G.

Let's start

- Make sure you have fastboot drivers installed (if you managed to soft-brick it you probably have them already installed, otherwise you can get them here)

- Download and extract this

- Reboot your phone in fastboot mode (keep Volume Down and Power buttons pressed for about 5 seconds then release the power button) and plug it to the PC

- Open the extracted folder and run "GPE_XT1032_KOT49H.M004_CFC.bat". Wait for it to finish (ignore errors, they're normal), then reboot to bootloader again (choose Normal powerup and keep pressed Volume Down until it boots to bootloader again)

- Download and extract this (mirror)

- Open the extracted folder and run THE FILE "fastboot flash recovery recovery.img.bat" (poorly chosen filenames, I know)

- Wait for it to finish, then choose "Recovery" item in bootloader and let it reboot to recovery.

- Go to "mounts and storage" and select "format cache", confirm, then select "format /data and /data/media", confirm.

- Go back to main menu and select "wipe data/factory", confirm.

- Return to the folder and run the file "adb push a.zip sdcard a.zip.bat", let it finish (it will take a couple of minutes, the window will close itself when done).

- From recovery select "install zip", then "choose zip from sd card" and select "a.zip". Let it finish, then go back to main menu and choose "power options", then "reboot to bootloader"

- Download and extract this (mirror)

- Open the extracted folder and run "flashall.bat". You should see no error (I got an error while it was flashing recovery but this is not important, what you should notice is that all the errors you got before are gone). Let it finish, then give it some time to boot.

Enjoy

You're done. Now you should have a stock 4.4.2 retail EU moto g. At this point you can flash the rom you want (for example, I flashed the original retail de, since my phone is german) without getting errors

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More or less I followed this, but I wrote the exact steps I made, I fixed wrong commands and uploaded a more complete version for last file