A couple of suggestions:
1 - Do a crontab -e from a root login to make sure you didn't included it there by accident.
2 - Make sure that it is not included in the OMV scheduled tasks from the gui.
I'm pretty sure that these are not the cause, but it doesn't cost anything to check.
Other than that it would seem to be a anacron issue. Perhaps you can create a script that doesn't do anything (maybe touch a file) and include it in the weekly folder and see if it gets executed as well as the balance (you should get an email).