Drobo 5d with 5 red lights on the drives!

My drobo 5D has suddenly decided that two many drives have been removed (non have) and that they have all failed. I have had drives fail in the past and replaced them but this seems more unlikely to be the drive themselves and more the Drobo itself having some issue.
The drobo reboots itself every so often and sometimes goes into a backup cycle, but then after a while ejects itself and crashes back to the 5 red lights, with the top one flashing.
Does this sound like something that other people have experienced and if so what can I do to get the drobo back up and running again.