[Q] Flashing stock Android 5.0.2 image to Nexus 7 [2012], stuck at 'writing system' topic

So my Nexus 7 (2012, wifi only, 32 GB, Android 4.4.4, not rooted) is just over a year old, and I have had absolutely no problems with it until one fine day its battery was completely drained and even after charging it for over 3 hours, it refused to boot up. It was stuck at the 4 colored balls animation. I checked the bootloader and it said something like

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unable to mount /cache (invalid <something>)

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.
So I decided that since I will anyway have to do a complete wipe of the data on tablet, why not install Android 5.0.2 by getting the image from Google? But much to my chagrin, the command prompt has been stuck on

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writing 'system' . . .

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for almost an hour now. --Shouldn't the whole process be complete in 10 minutes tops?
Another thing is that adb does not detect my device, but fastboot does.
Also, the command,

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fastboot flash bootloader bootloader-grouper-4.23.img

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throws an error:

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writing bootloader . . .
FAILED (remote: (InvalidState))

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What could be the error? Is it an H/W issue? Or am I simply doing something wrong?
The commands I gave are:

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fastboot oem unlock
fastboot erase boot
fastboot erase cache
fastboot erase recovery
fastboot erase system
fastboot erase userdata
fastboot flash bootloader bootloader-grouper-4.23.img
fastboot -w update image-nakasi-lrx22g.zip

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Attached Thumbnails

 

Ota for my 2012 nexus7 16 gb topic

I know that this question has been asked a 100 times probably but I am just curious about when I should be getting the new update to lollipop 5.0.1 or will we even get it now THANK YOU FOR YOUR HELP B.T.W. my NEXUS7 is completely stock I've never done anything to it THANKS AGAIN FOR YOUR HELP! GOD BLESS!!!

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