[Moto G4 Plus Questions & Answers] echo92:
If you previously were on the March 2017 security build (should be NPJS25.93-14.4), you may wish to download this stock ROM, which is the latest build that we have available (NPJS25.93-14.4, March 2017 security patch). https://xdaforums.com/moto-g4-plus/how-to/stock-rom-npjs25-93-14-4-march-1-t3608138 This stock ROM thread also has scripts to help you flash, though you may wish to edit them to match the commands below. You may also verify if you're on the latest firmware previously by booting to your bootloader - I recall the March 2017 bootloader version is B1.05.

Regardless, you're likely getting that pre-flash validation error due to an attempt of flashing an older bootloader and/or attempting to relock your bootloader with an older firmware. You can only relock your bootloader with firmware of the same build you had previously or newer.

I'd suggest using the latest stock firmware, and provided you were on the March 2017 update previously, omit flashing the GPT and bootloader partitions (whether you're using the latest stock build or your November build - just keep those partitions as they are):

fastboot flash partition gpt.bin
fastboot flash bootloader bootloader.img

You may also wish to omit the locking commands if you don't wish to lock your bootloader. Your commands should look therefore like:

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 erase customize (optional: will erase any customizations if ordered through motomaker)
fastboot erase clogo (optional: will erase the custom boot logo if ordered through motomaker)
fastboot reboot

If you wish to relock your bootloader, use the commands as follows (if the commands complain of needing a signed image, try booting into your flashed stock system, toggle OEM Unlock in Developer Settings and re-flash the stock ROM with the re-locking commands)

fastboot oem lock begin
fastboot oem lock begin
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 erase customize (optional: will erase any customizations if ordered through motomaker)
fastboot erase clogo (optional: will erase the custom boot logo if ordered through motomaker)
fastboot oem lock
fastboot reboot

I've used the 1st list of flashing commands - the non-locking version - to revert from RR 5.8.3 27/05/2017 to the stock NPJS25.93-14.4 ROM on my XT1642 without issue (apart from the unlocked bootloader warning). Be aware that re-flashing a stock ROM will wipe your device clean (including internal storage) and may result in your SD card being non-functional until wiped. Back up your important data accordingly (you may wish to use Titanium Backup to preserve your app data), and transfer backups off your device until you have flashed.

EDIT - tweaked a couple of sentences for clarity.