Necesito ayuda Moto g4 FullBrick

[Elgauchito]

Hola, me trajeron un celular moto g4 para ver si lo podia salvar, no me supieron decir que fue lo que hicieron. El telefono enciende y no pasa de la pantalla de advertencia del bootloader

Your device has been unlocked and can't be trusted
To learn more visit:
motorola.com/unlockbootloader
ID:bad key
Your device will boot in 5 seconds.

asi se repite el mensaje cada 5 segundos en un loop infinito
se puede entrar en fast-boot mode

instale los drivers de motorola y la pc lo reconoce
tengo instalado android studio con los sdk y platform-tools con adb y fastboot

C:\Users\Marce\AppData\Local\Android\Sdk\platform-tools>fastboot devices
ZY223FFBZJ      fastboot

el comando getvar arroja esto:

C:\Users\Marce\AppData\Local\Android\Sdk\platform-tools>fastboot getvar all
(bootloader) version: 0.5
(bootloader) version-bootloader: moto-msm8952-B1.07
(bootloader) product: athene_13mp
(bootloader) board: athene_13mp
(bootloader) secure: yes
(bootloader) hwrev: P2A
(bootloader) radio: 5
(bootloader) storage-type: emmc
(bootloader) emmc: 16GB SAMSUNG QE13MB RV=08 PV=07 FV=0000000000000007
(bootloader) ram: 2GB SAMSUNG LP3 DIE=8Gb M5=01 M6=05 M7=00 M8=1F
(bootloader) cpu: MSM8952
(bootloader) serialno: ZY223FFBZJ
(bootloader) cid: 0x0032
(bootloader) channelid: 0x1a
(bootloader) uid: 37E01A0100000000000000000000
(bootloader) securestate: flashing_unlocked
(bootloader) iswarrantyvoid: yes
(bootloader) max-download-size: 536870912
(bootloader) reason: Volume down key pressed
(bootloader) imei: :ola:
(bootloader) meid:
(bootloader) date: 09-16-2016
(bootloader) sku: XT1621
(bootloader) battid: SNN5970A
(bootloader) iccid:
(bootloader) cust_md5:
(bootloader) max-sparse-size: 268435456
(bootloader) current-time: "Tue May 17 18:59:30 UTC 2016"
(bootloader) ro.build.fingerprint[0]: motorola/athene/athene:6.0.1/MPJ24
(bootloader) ro.build.fingerprint[1]: .139-23.4/4:user/release-keys
(bootloader) ro.build.version.full[0]: Blur_Version.24.24.4.athene.retai
(bootloader) ro.build.version.full[1]: l.en.US
(bootloader) ro.build.version.qcom: LA.BR.1.3.3-02720-8976.0
(bootloader) version-baseband: M8952_70004.04.03.32R ATHENE_LATAM_CUST
(bootloader) kernel.version[0]: Linux version 3.10.84-gcf01273 (hudsoncm
(bootloader) kernel.version[1]: @ilclbld30) (gcc version 4.9.x-google 20
(bootloader) kernel.version[2]: 140827 (prerelease) (GCC) ) #1 SMP PREEM
(bootloader) kernel.version[3]: PT Sat May 14 20:58:01 CDT 2016
(bootloader) sbl1.git: git=MBM-NG-VB1.07-0-g57d1343
(bootloader) rpm.git: git=MBM-NG-VB1.06-0-ga970ead
(bootloader) tz.git: git=69dd24b-dirty
(bootloader) hyp.git: git=69dd24b-dirty
(bootloader) keymaster.git: git=69dd24b-dirty
(bootloader) cmnlib.git: git=69dd24b-dirty
(bootloader) aboot.git: git=MBM-NG-VB1.07-0-gf9b89ba
(bootloader) qe: qe 1/1
(bootloader) frp-state: protected (77)
(bootloader) ro.carrier: retar
all: listed above
Finished. Total time: 0.109s

Probe con varias stock roms y siempre es lo mismo
la ultima que probe es :
ATHENE_NPJS25.93-14-18_cid50_subsidy-DEFAULT_regulatory-DEFAULT_CFC.info
en todas me pone: image signed with key bad key

C:\Users\Marce\AppData\Local\Android\Sdk\platform-tools>fastboot flash boot boot.img
(bootloader) has-slot:boot: not found
Sending 'boot' (16384 KB)                          OKAY [  0.844s]
Writing 'boot'                                     (bootloader) Image signed with key bad key

OKAY [  0.563s]
Finished. Total time: 1.610s

C:\Users\Marce\AppData\Local\Android\Sdk\platform-tools>fastboot flash recovery recovery.img
(bootloader) has-slot:recovery: not found
Sending 'recovery' (16484 KB)                      OKAY [  0.828s]
Writing 'recovery'                                 (bootloader) Image signed with key bad key

OKAY [  0.609s]
Finished. Total time: 1.625s

alguien por favor me podria decir que pasa o si ya no hay solucion para esto
hace mas de una semana que estoy leyendo tutoriales, buscando en varias paginas y no encuentro solucion.