Ceph datastore host parse error

Recently we are facing an issue with ceph datastore in OpenNebula. In Ceph datastore, ceph-host section we previously added as "CEPH_HOST = “mon1 ceph1 ceph2 ceph3 ceph6"” which works properly. But now a day whenever I am trying to deploy/migrate/ an vm to CEPH datastore generating an error of “unable to parse address in ‘mon1:6789;ceph1:6789;ceph2:6789;ceph3:6789;ceph6:6789’” though from system all address are resolved.

I have resolved this issue by replacing the hostname using IP and then all operations work properly. But why such happening??

What is your Ceph version?

I am using ceph nautilus version and already integrated with the OpenNebula 5.8 version. Previously there is no issue with adding host but getting an error now.