DFS replication may suddenly not work as expected and you need some ways to check its status and to further fix it if possible.
dfsrdiag is a diagnostic tool that can be run on the DFS server to help give diagnostic information.
dfsrdiag ReplicationState will give you the current file replication status.
dfsrdiag Backlog gives information about the consistency between member of the replication group.
The Event Viewer on the DFS server can also give information about the DFS application. Event ID 2213 is an error/warning that will be logged if the DFS server unexpectedly shutsdown. When it happens, the DFS replication will not be resumed (default) and it needs manual intervention to resume the replication using the instruction in the event log description to use the wmic command to call ResumeReplicate on the dfsrVolumeConfig.