I received a bricked Nexus 5, trying to get it running

It was supposedly completely bricked.
Tried various ways to manage to get it running but failed. Now i am turning to you guys.
I can fastboot it.
I was able to test SDRAM and EMMC with BoardDiag and it looks to be okay
More details:

Code:

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C:\adb>fastboot getvar all
(bootloader) version-hardware: rev_11
(bootloader) version-baseband: M8974A-2.0.50.2.26
(bootloader) version-bootloader: HHZ11n
(bootloader) version-cdma: N/A
(bootloader) variant: hammerhead D821(H) 16GB
(bootloader) serialno:(redacted)
(bootloader) carrier: None
(bootloader) secure-boot: yes
(bootloader) unlocked: yes
(bootloader) product: hammerhead
(bootloader) partition-size:aboot: 80000
(bootloader) partition-type:aboot: emmc
(bootloader) partition-size:boot: 1600000
(bootloader) partition-type:boot: emmc
(bootloader) partition-size:recovery: 1600000
(bootloader) partition-type:recovery: emmc
(bootloader) partition-size:system: 40000000
(bootloader) partition-type:system: ext4
(bootloader) partition-size:userdata: 3321fa800
(bootloader) partition-type:userdata: ext4
(bootloader) partition-size:cache: 2bc00000
(bootloader) partition-type:cache: ext4
(bootloader) partition-size:persist: 1000000
(bootloader) partition-type:persist: ext4
all:
finished. total time: 0.297s

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When i try to flash stock via fastboot i get:

Code:

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sending 'bootloader' (3119 KB)...
OKAY [  0.874s]
writing 'bootloader'...
FAILED (remote: invalid bootloader image
)
finished. total time: 1.062s
rebooting into bootloader...
OKAY [  0.110s]
finished. total time: 0.110s
< waiting for device >
sending 'radio' (45425 KB)...
OKAY [  9.734s]
writing 'radio'...
OKAY [  3.110s]
finished. total time: 12.844s
rebooting into bootloader...
OKAY [  0.095s]
finished. total time: 0.109s
< waiting for device >
archive does not contain 'boot.sig'
archive does not contain 'recovery.sig'
failed to allocate 1046266608 bytes
error: update package missing system.img
Press any key to exit...

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I cannot find much info on the Bootloader that is installed
Any advice?