The Registry on the Target Core has a second Source Core entry without a Hostname or Globally Unique Identifier (GUID).
When you expand both entries, the agent list is either the same or has several of the same agent GUIDs. Agents are not allowed to be replicated from independent Source Cores to the same Target Core with the same Agent GUID. The Agent GUID must be unique to correctly identify the agent. LMU struggles with the GUID duplication and does not display what agents are replicated to the Target Core.