Unable to log into web gui after update

Just an update. I went through all files located in /var/lib/docker/overlay2 and there was no files larger than 620M (3.2G) and certainly not adding up to anywhere near 100GB . I then proceeded to stop the Plex docker, remove it and run another docker prune just to ensure that wasn't the problem. I am still in the same position and there is still no space on the 'Boot Drive' even though Plex has been removed from the system. What could possibly be taking up the space on the boot drive?

The output of sudo du -d1 -x -h / | sort -h

root@lh-omv-nas:~# sudo du -d1 -x -h / | sort -h
4.0K /export
4.0K /home
4.0K /lib64
4.0K /mnt
4.0K /sharedfolders
8.0K /media
12K /srv
16K /lost+found
16K /opt
76K /root
7.3M /etc
13M /bin
15M /sbin
173M /boot
950M /usr
1.2G /lib
1.4G /var
3.7G /

The output of df -h /

root@lh-omv-nas:~# df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/sdc1 110G 108G 0 100% /

The drive appears to have change for some reason to sdc1 as apposed to sdb1.

The full output of df -h:

root@lh-omv-nas:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 794M 9.2M 784M 2% /run
/dev/sdc1 110G 108G 0 100% /
tmpfs 3.9G 0 3.9G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
tmpfs 3.9G 0 3.9G 0% /tmp
/dev/sdb1 2.8T 12G 2.8T 1% /srv/dev-disk-by-label-Nextcloud
/dev/sde1 7.3T 234G 7.1T 4% /srv/dev-disk-by-label-Rsnapshot
/dev/sda1 2.8T 208G 2.6T 8% /srv/dev-disk-by-label-Docker
//192.168.10.246/RemoteBackup 7.3T 349G 7.0T 5% /srv/2b1385da-c097-4af7-8d5f-83da773d4b29
overlay 110G 108G 0 100% /var/lib/docker/overlay2/1bb93d795d93790555cade4c27f2b28765673b594ba15e4d5b7786044f450e4a/merged
overlay 110G 108G 0 100% /var/lib/docker/overlay2/28f5e6285cb6404702a61090a5f75eb3a05798888a2aa5d514e08f36a3a7dc1b/merged
overlay 110G 108G 0 100% /var/lib/docker/overlay2/dacfcb5422d6922a081bdf59ff3c5807375859a408da7be74762430cb28ee1a9/merged
overlay 110G 108G 0 100% /var/lib/docker/overlay2/2be799da1cd914fa2265839de5cc636d09462af966573a9d2a233aa5b7d64a84/merged
overlay 110G 108G 0 100% /var/lib/docker/overlay2/e0595ffea34c748296043761a2424a712c24450d1ed9258967f3ad64445e5947/merged
overlay 110G 108G 0 100% /var/lib/docker/overlay2/cdec3ba174225596ad44ba8215f81a9919ef7f042b23a5609a42be81bed26ffe/merged
overlay 110G 108G 0 100% /var/lib/docker/overlay2/33b3d671e34abc938e64383c4007b5cf38c8781811b427a88f14bba0ab83d2d2/merged
shm 64M 0 64M 0% /var/lib/docker/containers/5a8410a44e40c83d085bb8f81f0f0d86d93c434e3cf048862249c37d74a75103/mounts/shm
shm 64M 0 64M 0% /var/lib/docker/containers/35f81b915c9e6d75ba42f56510305d34d564b71f3d71200e3f925d5c2d31b2d8/mounts/shm
shm 64M 0 64M 0% /var/lib/docker/containers/83679895de479f3b7ae17ccc7e413d4572782d0b1be38830c182fb4469a3fd38/mounts/shm
shm 64M 0 64M 0% /var/lib/docker/containers/071aff54b9075a0af3a6980d10d0e3a0699eb61869341bdac7a5f61713e20ae8/mounts/shm
shm 64M 0 64M 0% /var/lib/docker/containers/c5b1c11399dcbf41804aa98c685ea3c6ae17cdee314b0c4ca642449bb9be60e7/mounts/shm
shm 64M 0 64M 0% /var/lib/docker/containers/e69a6ee3537c48c7d721119c7d67e2eee440caaa25db40687f6cdd3f2d042852/mounts/shm
shm 64M 0 64M 0% /var/lib/docker/containers/f04dfe06d693b0a67796294f791402aec59b3696b72e5ced9027d2c0725d06c6/mounts/shm

blkid output:

root@lh-omv-nas:~# blkid
/dev/sda1: LABEL="Docker" UUID="e1563c34-77b8-4332-bf39-e64bb930389c" UUID_SUB="1c425899-894d-478d-8f8f-19cf6c7ccb55" TYPE="btrfs" PARTUUID="b8ae89ee-24d2-4c1a-8258-04bc0317d137"
/dev/sdb1: LABEL="Nextcloud" UUID="579d4d87-6c71-47bd-96f5-4241e4ab5d74" UUID_SUB="951f9b65-18f1-41b3-9f0d-4eb0a3e71342" TYPE="btrfs" PARTUUID="b3cc046c-eda0-4b02-a440-dc3467d36170"
/dev/sde1: LABEL="Rsnapshot" UUID="a1fab608-3891-44e4-9437-74c7de457d17" UUID_SUB="2354a522-96b4-4269-b9a4-595534fe85f8" TYPE="btrfs" PARTUUID="8e5200ec-1ad7-429a-ae66-e1c13c6a2620"
/dev/sdc1: UUID="6cab88f3-a43d-4489-b0ca-30d48f16e623" TYPE="ext4" PARTUUID="dee338c9-01"
/dev/sdc5: UUID="fb892647-b833-40b0-92af-d601a036bf2c" TYPE="swap" PARTUUID="dee338c9-05"

edit: btrfs is only on the shared drives not on the boot drive.

@ryecoaaron I have rebooted the system numerous times. I have just shut it down now and pulled the plug just to make sure. The problem still exists.

It is installed on a Corsair Voyager GTX 128GB usb HDD.

The output of tune2fs -l /dev/sdc1

root@lh-omv-nas:~# tune2fs -l /dev/sdc1
tune2fs 1.44.5 (15-Dec-2018)
Filesystem volume name: <none>
Last mounted on: /
Filesystem UUID: 6cab88f3-a43d-4489-b0ca-30d48f16e623
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent 64bit flex_bg sparse_super large_file huge_file dir_nlink extra_isize metadata_csum
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 7290880
Block count: 29163075
Reserved block count: 1458153
Free blocks: 405302
Free inodes: 7154689
First block: 0
Block size: 4096
Fragment size: 4096
Group descriptor size: 64
Reserved GDT blocks: 1024
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
RAID stripe width: 8191
Flex block group size: 16
Filesystem created: Sun Oct 7 10:27:51 2018
Last mount time: Wed Mar 27 18:01:27 2019
Last write time: Wed Mar 27 18:01:23 2019
Mount count: 92
Maximum mount count: -1
Last checked: Sun Oct 7 10:27:51 2018
Check interval: 0 (<none>)
Lifetime writes: 467 GB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 32
Desired extra isize: 32
Journal inode: 8
First orphan inode: 6952315
Default directory hash: half_md4
Directory Hash Seed: 30e707c8-a770-4147-95f8-4ad0ef7f4b8a
Journal backup: inode blocks
Checksum type: crc32c
Checksum: 0xbbf3b2fb

Thanks @ryecoaaron I will give this a try when i get back later tonight.

edit: Ps I have found a file that appears to be 131GB located in /proc/kcore is this normal? I must have over 200+ new files created in /proc all created within 5 seconds of each other.

Thanks tkaiser. Just thinking out loud if I removed the storage drives would that be of any benefit?