This tip is for Android devices stuck in a boot loop after flashing Android stock image.
In my case, I was using the official backup from Google : https://developers.google.com/android/images
I noticed that I had a specific error at the end of the procedure :
Writing ‘userdata’ FAILED (remote: ‘Bogus size sparse and chunk header’)
If you are facing the same issue, try formatting the userdata partition and flash it separately.
I had the issue because I installed different OS on my device that altered my partitions.
Boot in bootloader mode with the buttons ON and Volume down –
Then format the partition:
fastboot format userdata mke2fs
Locate the userdata.img in your zip or source files, then flash it:
fastboot flash userdata userdata.img
Reboot the tablet, now it should boot correctly to the home page:
I hope this tip will save your time!