Email to admin: [FATAL ERROR] Lock already exists. Munin Dying

[FATAL ERROR] Lock already exists: /var/run/munin/munin-graph.lock. Dying.
at /usr/share/perl5/Munin/Master/GraphOld.pm line 404.

I have 10 mail boxes.

it’s a pretty frequent email message.

I have been transferring messages from an old imap email to the new MIAB installation via FTP.

Try rebooting the box?