Are you able to load the Console?
I would suggest going to the ‘Computers’ section, and filtering by ‘BES Relay Service Installed -> Yes…’ then looking at the DNS Name property of the Clients (you can add this as a column). Given the mention of ‘RelaysFileUpdater’, it seems the Root Server is failing to process these names (perhaps one is too long? at over greater than 64 characters?).
If none of the DNS Names look strange, check the value of the following setting on the Relays:
Note that this setting can also be used to override the DNS Name from a potentially problematic value.
Additionally, check to ensure that the Root Server can resolve each of the DNS Names of the Relays.