Every cronjob that I run logs an error.
* * * * * /usr/bin/wireguard_watchdog leads to:
cron.err crond[9024]: USER root pid 9184 cmd /usr/bin/wireguard_watchdog
This seems to have been an issue for over 14 years 
Not that it's super important, but running a cronjob every minute trashes the logfile.
I know. Install syslog-ng and filter that text!
Change option cronloglevel '5' in /etc/config/system to level 9.
See: https://openwrt.org/docs/guide-user/base-system/system_configuration#system_section
To be clear (since others haven't clearly noted it yet), the normal logging level in OpenWrt is Err.
There isn't an error.
It ain't a bug, it’s a feature.
Strange feature if you as me but I don’t think anyone really want to change it, mostly because the never ending worthless small flash routers must live on!?
If it ain't an error, why does it say error? Sounds like an error to me 
Good question.
That's simply the "logging level" in *nix-like systems. I'll have to search for the discussion where a developer noted there's only a few other options (e.g., "warn"). Other options imply severity.
Another option is to build OpenWrt firmware where it's capable of those log levels.
That's weird. Most systems allow for an "info" log level.
probably related to https://github.com/openwrt/luci/issues/7315
Question: would a crash or firewall warning (for example) be considered info?
The post was literally one down from what I linked:
The reason I switch to micrond if I need to use cronjobs on OpenWrt.
That seem to be a solution with busybox settings, but it requires building from source code.