Crontab specs which worked in the past can break when moved from one crontab file to another. Sometimes the reason is that you've moved the spec from a system crontab file to a user crontab file or vice-versa.
The cron job specification format differs between users' crontab files (/var/spool/cron/username or /var/spool/cron/crontabs/username) and the system crontabs (/etc/crontab and the the files in /etc/cron.d).
The system crontabs have an extra field 'user' right before the command-to-run.
This will cause errors stating things like george; command not found when you move a command out of /etc/crontab or a file in /etc/cron.d into a user's crontab file.
Conversely, cron will deliver errors like /usr/bin/restartxyz is not a valid username or similar when the reverse occurs.