Above Python script is not part of the original Pi-hole install:
pi@ph5b:~ $ stat /usr/local/bin/Pi-Hole-Monitoring.py
stat: cannot statx '/usr/local/bin/Pi-Hole-Monitoring.py': No such file or directory
Quick search and seems to belong to below (EDIT: or similar fork):
https://github.com/skoogee/ubuntu_pihole_monitor
The error could be related to recent database changes:
That github project doesn't allow to create an "issue" so I have no idea how to contact the maintainer(s) for that project to ask for help.