When configuring a connection, if the domain is not reachable, the source scope appears blank:
Then accessing the connection again it shows the default of checking everything off:
Steps to reproduce this issue:
1.- Create a new connection in the Synchronization Service
2.- Select a custom scope and save
3.- Disable connection to domain
4.- Open connection scope settings (scope will display blank)
5.- Click "Save and Continue"
Connection scope is cleared out. When the connection is restored to the domain, the scope is back to default where the entire domain is selected.