Hi,
So this is a known bug on CWMS 1.1: CSCui25358 Changing FQDN for VM gets hostname error.
There is a possible workaround for this:
-Change the DNS entry for the new FQDN you want to use to a non-existent IP address.
-Save the change you would like to make to the FQDN on CWMS.
-Change the DNS entry back to the correct IP address.
If this doesn’t help, you will unfortunately be forced to rebuild the system.
This bug will be fixed in CWMS 1.5 MR1 which is scheduled for release in early November.
Dejan