bbb-resync-freeswitch exited with return code 255

I'm getting an hourly cron email from bbb.webarch.org.uk like this:

From: Cron Daemon <root@bbb.webarch.org.uk> 
To: root@bbb.webarch.org.uk 
Subject: Cron <root@bbb>    cd / && run-parts --report /etc/cron.hourly                                                                                                      

run-parts: /etc/cron.hourly/bbb-resync-freeswitch exited with return code 255

We should try to work out if there is a problem causing this at some point.