This domain controller has an extremely high number of replication partners and is in danger of not being able to replicate in a timely fashion.
Review your directory replication design to decrease the number of replication partners for this domain controller.
This alert is commonly triggered by another domain controller failing, which causes the Knowledge Consistency Checker (KCC) to compute new optimal replication paths.
In this case, fix the failing domain controller and review your replication topology design to prevent future overloads in the event of a domain controller failure.