Can I safely flash back to stock Marshmallow?

[treela]

My Moto G4 came with Marshmallow installed and I performed an OTA update to Nougat. I then unlocked my bootloader and flashed some custom Nougat ROMs (7.1.2, so newer than the newest official available version). Now I want to get back to stock Nougat so I can relock the bootloader and all that jazz.

As far as I can tell, only Marshmallow firmware images are available so can I safely flash that (I'm thinking "ATHENE_MPJ24.139-23.4_cid50_subsidy-DEFAULT_CFC.zip") and then OTA to Nougat from there or will that cause problems because I already (presumably) have the Nougat bootloader version? I don't want to brick my phone!

Note I'm using a retail United Kingdom XT1622 Moto G4.

Cheers all in advance,
treela

 

[treela]

Ah ha! Found this:
https://forum.xda-developers.com/mo...owngrade-nougat-to-marshmallow-t3487201/page5

Got back to stock Marshmallow all OK

 

[zonggestsu]

flashing back to marshmallow and being able to relock the bootloader after doing the ota wont really work. best bet is to try and find the stock nougat image and flash it.

 

[hi_navneet]

flashing back to marshmallow and being able to relock the bootloader after doing the ota wont really work. best bet is to try and find the stock nougat image and flash it.

I was on Nougat and then i unlocked my bootloader and flash custom ROM and now when i try to flash stock nougat firmware, command result show PREFLASH VALIDATION FAILED SECURITY DOWNGRADE
What show i do now I'm was on Nougat and flashing Nougat firware but always failed.
Please tell me what to do.
Model : XT1624
Soory for bad english