[Moto G4 Plus Guides, News, & Discussion] echo92:
The command you've mentioned needs a bit of explanation - this particular method used Motorola's version of fastboot (called mfastboot), which is quite old, as reflected in the date of the opening post. The 'ignore gpt.bin' error mentioned is a warning you'll see if you try to downgrade your firmware either via mfastboot or via fastboot - the GPT, as well as bootloader, cannot be downgraded. If you attempt to flash an older version of the GPT or bootloader from the firmware to your device, your device should block the flash and alert you to a security downgrade error.

However, this failure to downgrade the GPT and bootloader to a previous version (to stop security holes being re-opened, I imagine), creates a scenario where using OTA updates becomes very risky. In brief, OTA updates check your system version, and apply the update, assuming your device firmware is at the same patch level. As you've downgraded your firmware (but NOT your GPT and bootloader), this assumption is not true, and so the OTA may apply an older bootloader version without checking, which appears to the main reason we've seen so many G4/Plus devices hardbricked in the past couple of years or so. Luckily, we have a blankflash to rescue such devices but I still cannot recommend downgrading for this reason. Using TWRP flashables, whilst requiring TWRP and an unlocked bootloader, would be safer since they do not affect the bootloader and may have the updater disabled.

If you still wish to downgrade using fastboot firmware (be warned this process will erase your device):

1)On your computer, verify you have minimal ADB/fastboot https://xdaforums.com/showthread.php?t=2317790 or a suitable ADB/fastboot installation and the Motorola USB drivers https://support.motorola.com/us/en/drivers Download the G4/Plus (athene) firmware you wish to downgrade to, extract the firmware and copy the files to your ADB/fastboot folder.

1a)Confirm your computer can connect to your device by connecting your device to your computer by USB, then booting your device to the bootloader. Open an ADB terminal and type 'fastboot devices' without quotes into the ADB terminal and press Enter. You should get a response from your device with its serial number.

2)If your device bootloader is not yet unlocked, unlock the bootloader following the instructions from Motorola https://motorola-global-portal.custhelp.com/app/standalone/bootloader/unlock-your-device-a As warned, this process will erase your device

3)Once unlocked (or already unlocked), boot your device to the bootloader and connect your device to your computer. You do not need TWRP for these next steps. Open an ADB terminal when your device is booted to the bootloader, and copy paste the following commands in order, line by line, pressing Enter to execute each command and waiting until the command completes before proceeding:

fastboot flash logo logo.bin
fastboot flash boot boot.img
fastboot flash recovery recovery.img
fastboot flash dsp adspso.bin
fastboot flash oem oem.img
fastboot flash system system.img_sparsechunk.0
fastboot flash system system.img_sparsechunk.1
fastboot flash system system.img_sparsechunk.2
fastboot flash system system.img_sparsechunk.3
fastboot flash system system.img_sparsechunk.4
fastboot flash system system.img_sparsechunk.5
fastboot flash system system.img_sparsechunk.6
fastboot flash system system.img_sparsechunk.7
fastboot flash modem NON-HLOS.bin
fastboot erase modemst1
fastboot erase modemst2
fastboot flash fsg fsg.mbn
fastboot erase cache
fastboot erase userdata
fastboot reboot

These commands omit the OEM locking commands, as well as flashing the GPT/bootloader. When you execute the last command, reboot, your device should be downgraded to the firmware that you copied to your ADB folder. You are welcome to make an executable script of these commands, I prefer to enter the commands in manually to monitor the progress of the flash.

As mentioned previously, DO NOT use OTA updates when downgraded. If you wish to attempt to stop the Motorola update services, you'll need a root solution like magisk, and check this thread for help https://xdaforums.com/moto-g4-plus/help/how-disable-notification-update-t3459587