dual boot - GParted resize partition Error - e2fsck: Possibly non-existent device?

Aim:

Grow / Extend Linux root and home partition using GParted on live Ubuntu

Error:

Root partition failing file system check and repair

GParted 0.25.0 --enable-libparted-dmraid --enable-online-resize
Libparted 3.2
Grow /dev/sda8 from 18.63 GiB to 48.83 GiB  00:00:04    ( ERROR )
calibrate /dev/sda8  00:00:04    ( SUCCESS )
path: /dev/sda8 (partition)
start: 427542528
end: 466604031
size: 39061504 (18.63 GiB)
check file system on /dev/sda8 for errors and (if possible) fix them  00:00:00    ( ERROR )
e2fsck -f -y -v -C 0 /dev/sda8  00:00:00    ( ERROR )
Possibly non-existent device?
e2fsck 1.43.3 (04-Sep-2016)
e2fsck: No such file or directory while trying to open /dev/sda8
========================================

System info:

Dual-boot - Linux Mint 18 + Windows 10

GParted Screenshot Link http://imgur.com/cv3N6mM

Steps I have followed:

1. Allocated free space from windows' C drive


2. Booted from Ubuntu live USB


3. Launched GParted


4. Turned swap off


5. Moved my root partition ext4[/dev/sda8] to the left of unallocated space


6. Right click on ext4[/dev/sda8] - Check and repair filesystem ext4[/dev/sda8]


7. Check ext4[/dev/sda8] successful


8. Resize/Move ext4[/dev/sda8] to 48.23 GB - Apply


9. ERROR!

What I have found:

1. Bad Superblock Problem?


2. Logical Partition table problem?

Please Help!

Apparently I was able to resize the root "/" partition while my OS was running and "/" was mounted.

Root file system /dev/sda8 extended to 48.83 GB:
http://imgur.com/lINIUwn

Contrary to what I read everywhere on GParted official docs and forums, it is possible. I have restarted my system and verified it using disk-usage-analyser & gnome-disk utility.

Anyone knows how was this was possible?
I'm willing to share further details.