Not exactly solved, but I’ve got a workaround.
- I removed the “.sh” suffix, and added #!/bin/sh to the start of the file to let cron know it’s a shell executable.
- I then moved the script into /etc/periodic/hourly, so it now it runs on an hourly basis.
It’s not perfect, but does the job I need. I’d still like to know how to set it up as a cron job though if anyone has any ideas.