This article helps to explain how SD-Cloud is designed to handle Shared objects like Addresses, services etc.
Current behavior in SDC is -> an object say ABC has values 123 and in use in a particular FW policy..
We had a similar bug reported by our internal teams to Juniper SDC cloud Engg team where import gets stuck or hunged with large number of objects in the Firewall/SRX..
But for now, this is as per the current design limitation.
Please contact JTAC for any queries or support.