First point, you're question, aside problem you're facing, is an interesting one: Zentyal targeting SMBs where we will have potentially often people not knowing Linux command line, how to investigate such problem using Zentyal itself?
Then I would rather try first to debug this problem before applying workaround.
Once you have command line (either via console or connecting through SSH), can you have a look at /var/log/ebox/ and search for related message in ebox.log. You can have a look also at error.log but, as there is no timestamps there, it's more difficult.
If there is nothing obvious in /var/log/ebox/ebox.log, look also at /var/log/syslog