/var/log is used for a variety of things (including backups).
The fact this filesystem is not mounted means anything written to /var/log will actually be on the root filesystem.
With only 50gb allocated to the root filesystem, a backup will never successfully complete.
Which means, ultimately, you need to solve the problem of why /var/log isn't mounting.
You can try something like an fsck -y /var/log to see what happens (will repair all errors).
To preserve the existing contents of /var/log, you probably need to do something like:
mv /var/log /var/log.old
mkdir -m 755 /var/log
chown admin:root /var/log
Then try and mount again.
If none of this works, I suggest engaging with the TAC.