flock () on closed filehandle LOCK_FILE in / usr / bin / apt-mirror

I recently upgraded an Ubuntu 16.04 virtual machine to 18.04. I regularly use this virtual machine to run apt-mirror at school on their broadband internet connection, then rsync these files on my home rackmount server to update multiple computers to the home without losing the small amount of bandwidth that I have there. Since the update, can not run apt-mirror on my virtual machine. He continues to give the error:

flock () on closed filehandle LOCK_FILE on line / usr / bin / apt-mirror 214

immediately followed by:

apt-mirror is already running, quit at line / usr / bin / apt-mirror 217

apt-mirror is NOT running and has no cron job. I've tried to reboot and I even tried to delete the old lock file, but I guess this method is no longer used. Is there a way to force unlocking to run apt-mirror?