Unity Connection Intra-Site Networking Stalled

In some situations when adding server(s) to Unity Connection's intra-site networking, replication can get stuck and constantly show errors on the Voice Network Map. Symptoms include not seeing other server's partitions, search spaces, users, distribution lists, etc. Looking at the traces for Connection Digital Networking Replication Agent service shows many entries like "18:34:13.772 |20016,StalledReplicationDetector,,-1,-1,Detected stalled replication sending to location <location name>. Waiting for acknowledgment of USN <number>. This situation may indicate network connectivity problems."
Follow these steps to get replication unstuck:

Remove the stuck servers from Locations via "remove self from site".

On all servers restart the following services:
Connection Digital Networking Replication Agent
Connection SMTP Server

Add the servers back, don't forget to put in the Connection Location Passwords on all servers & activate the Connection Digital Networking Replication if necessary.