@silmathoron Looks like both work but I was unaware of that option! I don't see much call for starting at a specific minute and then every X minutes after that, it's usually either or but I'm glad it's there for someones use case!
If you are running everything as a systemd service then you should be able to match up the erratic behaviour with what's causing it in journalctl, if you have set up logging for that bit anyhow. Good luck with the debugging! =]