Full reboots are not recommended like this. I think you are already aware of this so here's an answer to your question.
I suspect that your problem is that the
contrab -e command is designed for a user to add their own cron scripts. It's not generally used for adding system (root) cron entries.
I believe you would be better to manually add a file in
/etc/crontab.d/ or even add an entry in