A bridgehead server is a domain controller in each site, which is used as a contact point to receive and replicate data between sites. For inter-site replication, KCC designates one of the domain controllers as a bridgehead server. In case the server is down, KCC designates another one from the domain controller. When a bridgehead server receives replication updates from another site, it replicates the data to the other domain controllers within its site.
Repadmin Sync: (Synchronizes DC with replication partners)
Bridgehead Servers: (Displays bridgehead servers)
Seeing a number of KCC replication errors in the event log, no doubt there is something not configured correctly in “Site-&-Services” This Microsoft document should give you a few tips. Troubleshoot with Repadmin