It is always a struggle configuring a cronjob to run certain scripts; there is always a mis configuration, a PATH, an environment variable that is different from when you use it in interactive mode, etc… Do you have any tricks to avoid or minimize those issues?
Wrap all the cron job tasks in a bash script and make sure it works. Call the script directly in the cron configuration. Dump the output of the cronjob to a logfile. Set it up to run every minute so you can ensure it works via the cron environment.