When I tried to do a factory reset, the tablet would only boot to recovery (TWRP) - I couldn't even turn it off. I had to (meaning somebody else had to, since I don't have any access to Windoze) restore everything using the official app. The problem seemed to come from some partition mismatch. From the recovery log (for the backup which partially failed).
I:Setting up '/data' as data/media emulated storage.
I:Can't probe device /dev/block/mmcblk0p24
I:Unable to mount '/data'
I:Actual block device: '/dev/block/mmcblk0p24', current file system: 'ext4'
I:Can't probe device /dev/block/mmcblk0p24
Failed to mount '/data' (Invalid argument)
I:Actual block device: '/dev/block/mmcblk0p24', current file system: 'ext4'
Unable to recreate /data/media folder.
I:Backup folder set to '/data/media/TWRP/BACKUPS/T10E3C5'
I:Settings storage is '/data/media'
Updating partition details...
I:Can't probe device /dev/block/mmcblk0p24
Failed to mount '/data' (Invalid argument)
I:Actual block device: '/dev/block/mmcblk0p24', current file system: 'ext4'
I:Unable to mount '/usbotg'
I:Actual block device: '', current file system: 'auto'
...done
I:Can't probe device /dev/block/mmcblk0p24
I:Unable to mount '/data'
I:Actual block device: '/dev/block/mmcblk0p24', current file system: 'ext4'
Unable to mount storage
I:Unmounting main partitions...
And then at the end of recovery.log
I:Can't probe device /dev/block/mmcblk0p24
Failed to mount '/data' (Invalid argument)
I:Actual block device: '/dev/block/mmcblk0p24', current file system: 'ext4'
Backup Failed. Cleaning Backup Folder.
Hi, how did you resolve it now? Using Windows? Have the same issue, data is somehow corrupted, changing fs doesn't help.